HTML 5

4.10 Forms

Forms allow unscripted client-server interaction: given a form, a user can provide data, submit it to the server, and have the server act on it accordingly (e.g. returning the results of a search or calculation). The elements used in forms can also be used for user interaction with no associated submission mechanism, in conjunction with scripts.

Mostly for historical reasons, elements in this section fall into several overlapping (but subtly different) categories in addition to the usual ones like flow content, phrasing content, and interactive content.

A number of the elements are form-associated elements, which means they can have a form owner and, to expose this, have a form content attribute with a matching form DOM attribute.

The form-associated elements fall into several subcategories:

Submittable elements

Denotes elements that can be used for constructing the form data set when a form element is submitted.

Resettable elements

Denotes elements that can be affected when a form element is reset.

Listed

Denotes elements that are listed in the form.elements and fieldset.elements APIs.

Labelable

Denotes elements that can be associated with label elements.

In addition, some submittable elements can be, depending on their attributes, buttons. The prose below defines when an element is a button. Some buttons are specifically submit buttons.

The object element is also a form-associated element and can, with the use of a suitable plugin, partake in form submission.

4.10.1 The form element

Categories

Flow content.

Contexts in which this element may be used:

Where flow content is expected.

Content model:

Flow content, but with no form element descendants.

Content attributes:

Global attributes

accept-charset

action

autocomplete

enctype

method

name

novalidate

target

DOM interface:

[Callable=namedItem]
interface HTMLFormElement : HTMLElement {
           attribute DOMString acceptCharset;
           attribute DOMString action;
           attribute boolean autocomplete;
           attribute DOMString enctype;
           attribute DOMString method;
           attribute DOMString name;
           attribute boolean novalidate;
           attribute DOMString target;

  readonly attribute HTMLFormControlsCollection elements;
  readonly attribute long length;
  [IndexGetter] any item(in DOMString name);
  [NameGetter=OverrideBuiltins] any namedItem(in DOMString name);

  void submit();
  void reset();
  boolean checkValidity();

  void dispatchFormInput();
  void dispatchFormChange();
};

The form element represents a collection of form-associated elements, some of which can represent editable values that can be submitted to a server for processing.

The accept-charset attribute gives the character encodings that are to be used for the submission. If specified, the value must be an ordered set of unique space-separated tokens, and each token must be the preferred name of an ASCII-compatible character encoding. [IANACHARSET]

The name attribute represents the form's name within the forms collection. The value must not be the empty string, and the value must be unique amongst the form elements in the forms collection that it is in, if any.

The autocomplete attribute is an enumerated attribute. The attribute has two states. The on keyword maps to the on state, and the off keyword maps to the off state. The attribute may also be omitted. The missing value default is the on state. The off state indicates that by default, input elements in the form will have their resulting autocompletion state set to off; the on state indicates that by default, input elements in the form will have their resulting autocompletion state set to on.

The action, enctype, method, novalidate, and target attributes are attributes for form submission.

The autocomplete and name DOM attributes must reflect the respective content attributes of the same name.

The acceptCharset DOM attribute must reflect the accept-charset content attribute.

The elements DOM attribute must return an HTMLFormControlsCollection rooted at the Document node, whose filter matches listed elements whose form owner is the form element, with the exception of input elements whose type attribute is in the Image Button state, which must, for historical reasons, be excluded from this particular collection.

The length DOM attribute must return the number of nodes represented by the elements collection.

The indices of the supported indexed properties at any instant are the indicies supported by the object returned by the elements attribute at that instant.

The item(index) method must return the value returned by the method of the same name on the elements collection, when invoked with the same argument.

Each form element has a mapping of names to elements called the past names map. It is used to persist names of controls even when they change names.

The names of the supported named properties are the union of the names currently supported by the object returned by the elements attribute, and the names currently in the past names map.

The namedItem(name) method, when called, must run the following steps:

1. If name is one of the names of the supported named properties of the object returned by the elements attribute, then run these substeps:

   1. Let candidate be the object returned by the namedItem() method on the object returned by the elements attribute when passed the name argument.

   2. If candidate is an element, then add a mapping from name to candidate in the form element's past names map, replacing the previous entry with the same name, if any.

   3. Return candidate and abort these steps.

2. Otherwise, name is the name of one of the entries in the form element's past names map: return the object associated with name in that map.

If an element listed in the form element's past names map is removed from the Document, then its entries must be removed from the map.

The submit() method, when invoked, must submit the form element from the form element itself.

The reset() method, when invoked, must reset the form element.

If the checkValidity() method is invoked, the user agent must statically validate the constraints of the form element, and return true if the constraint validation return a positive result, and false if it returned a negative result.

If the dispatchFormInput() method is invoked, the user agent must broadcast forminput events from the form element.

If the dispatchFormChange() method is invoked, the user agent must broadcast formchange events from the form element.

4.10.2 The fieldset element

Categories

Flow content.

Listed form-associated element.

Contexts in which this element may be used:

Where flow content is expected.

Content model:

One legend element follwed by flow content.

Content attributes:

Global attributes

disabled

form

name

DOM interface:

interface HTMLFieldSetElement : HTMLElement {
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute DOMString name;

  readonly attribute DOMString type;

  readonly attribute HTMLFormControlsCollection elements;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);
};

The fieldset element represents a set of form controls grouped under a common name.

The name of the group is given by the first legend element that is a child of the fieldset element. The remainder of the descendants form the group.

The disabled attribute, when specified, causes all the form control descendants of the fieldset element to be disabled.

The form attribute is used to explicitly associate the fieldset element with its form owner. The name attribute represents the element's name.

The disabled DOM attribute must reflect the content attribute of the same name.

The type DOM attribute must return the string "fieldset".

The elements DOM attribute must return an HTMLFormControlsCollection rooted at the fieldset element, whose filter matches listed elements.

The willValidate, validity, and validationMessage attributes, and the checkValidity() and setCustomValidity() methods, are part of the constraint validation API.

Constraint validation: fieldset elements are always barred from constraint validation.

4.10.3 The label element

Categories

Flow content.

Phrasing content.

Interactive content.

Form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Phrasing content, but with no descendant labelable form-associated elements unless it is the element's labeled control, and no descendant label elements.

Content attributes:

Global attributes

form

for

DOM interface:

interface HTMLLabelElement : HTMLElement {
  readonly attribute HTMLFormElement form;
           attribute DOMString htmlFor;
  readonly attribute HTMLElement control;
};

The label represents a caption in a user interface. The caption can be associated with a specific form control, known as the label element's labeled control.

Unless otherwise specified by the following rules, a label element has no labeled control.

The for attribute may be specified to indicate a form control with which the caption is to be associated. If the attribute is specified, the attribute's value must be the ID of a labelable form-associated element in the same Document as the label element. If the attribute is specified and there is an element in the Document whose ID is equal to the value of the for attribute, and the first such element is a labelable form-associated element, then that element is the label element's labeled control.

If the for attribute is not specified, but the label element has a labelable form-associated element descendant, then the first such descendant in tree order is the label element's labeled control.

The label element's exact default presentation and behavior, in particular what its activation behavior might be, if anything, should match the platform's label behavior.

<label><input type=checkbox name=lost> Lost</label>

The form attribute is used to explicitly associate the label element with its form owner.

The htmlFor DOM attribute must reflect the for content attribute.

The control DOM attribute must return the label element's labeled control, if any, or null if there isn't one.

Labelable form-associated elements have a NodeList object associated with them that represents the list of label elements, in tree order, whose labeled control is the element in question. The labels DOM attribute of labelable form-associated elements, on getting, must return that NodeList object.

4.10.4 The input element

Categories

Flow content.

Phrasing content.

If the type attribute is not in the Hidden state: Interactive content.

Listed, labelable, submittable, and resettable form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Empty.

Content attributes:

Global attributes

accept

action

alt

autocomplete

autofocus

checked

disabled

enctype

form

height

list

max

maxlength

method

min

multiple

name

novalidate

pattern

placeholder

readonly

required

size

src

step

target

type

value

width

DOM interface:

interface HTMLInputElement : HTMLElement {
           attribute DOMString accept;
           attribute DOMString action;
           attribute DOMString alt;
           attribute boolean autocomplete;
           attribute boolean autofocus;
           attribute boolean defaultChecked;
           attribute boolean checked;
           attribute boolean disabled;
           attribute DOMString enctype;
  readonly attribute HTMLFormElement form;
           attribute DOMString height;
           attribute boolean indeterminate;
  readonly attribute HTMLElement list;
           attribute DOMString max;
           attribute long maxLength;
           attribute DOMString method;
           attribute DOMString min;
           attribute boolean multiple;
           attribute DOMString name;
           attribute boolean noValidate;
           attribute DOMString pattern;
           attribute DOMString placeholder;
           attribute boolean readOnly;
           attribute boolean required;
           attribute unsigned long size;
           attribute DOMString src;
           attribute DOMString step;
           attribute DOMString target;
           attribute DOMString type;
           attribute DOMString defaultValue;
           attribute DOMString value;
           attribute DOMTimeStamp valueAsDate;
           attribute float valueAsNumber;
  readonly attribute HTMLOptionElement selectedOption;
           attribute DOMString width;

  void stepUp(in long n);
  void stepDown(in long n);

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;
};

The input element represents a typed data field, usually with a form control to allow the user to edit the data.

The type attribute controls the data type (and associated control) of the element. It is an enumerated attribute. The following table lists the keywords and states for the attribute — the keywords in the left column map to the states in the cell in the second column on the same row as the keyword.

The missing value default is the Text state.

Which of the accept, action, alt, autocomplete, checked, enctype, height, list, max, maxlength, method, min, multiple, novalidate, pattern, readonly, required, size, src, step, target, and width attributes apply to an input element depends on the state of its type attribute. Similarly, the checked, valueAsDate, valueAsNumber, list, and selectedOption DOM attributes, and the stepUp() and stepDown() methods, are specific to certain states. The following table is non-normative and summarises which content attributes, DOM attrbutes, and methods apply to each state:

When an input element's type attribute changes state, and when the element is first created, the element's rendering and behaviour must change to the new state's accordingly and the value sanitization algorithm, if one is defined for the type attribute's new state, must be invoked.

Each input element has a value, which is exposed by the value DOM attribute. Some states define an algorithm to convert a string to a number, an algorithm to convert a number to a string, an algorithm to convert a string to a Date object, and an algorithm to convert a Date object to a string, which are used by max, min, step, valueAsDate, valueAsNumber, stepDown(), and stepUp().

Each input element has a boolean dirty value flag. When it is true, the element is said to have a dirty value. The dirty value flag must be initially set to false when the element is created, and must be set to true whenever the user interacts with the control in a way that changes the value.

The value content attribute gives the default value of the input element. When the value content attribute is added, set, or removed, if the control does not have a dirty value, the user agent must set the value of the element to the value of the value content attribute, if there is one, or the empty string otherwise, and then run the current value sanitization algorithm, if one is defined.

Each input element has a checkedness, which is exposed by the checked DOM attribute.

Each input element has a boolean dirty checkedness flag. When it is true, the element is said to have a dirty checkedness. The dirty checkedness flag must be initially set to false when the element is created, and must be set to true whenever the user interacts with the control in a way that changes the checkedness.

The checked content attribute gives the default checkedness of the input element. When the checked content attribute is added, if the control does not have dirty checkedness, the user agent must set the checkedness of the element to true; when the checked content attribute is removed, if the control does not have dirty checkedness, the user agent must set the checkedness of the element to false.

The reset algorithm for input elements is to set the dirty value flag and dirty checkedness flag back to false, set the value of the element to the value of the value content attribute, if there is one, or the empty string otherwise, set the checkedness of the element to true if the element has a checked content attribute and false if it does not, and then invoke the value sanitization algorithm, if the type attribute's current state defines one.

Each input element has a boolean mutability flag. When it is true, the element is said to be mutable, and when it is false the element is immutable. Unless otherwise specified, an input element is always mutable. Unless otherwise specified, the user agent should not allow the user to modify the element's value or checkedness.

When an input element is disabled, it is immutable.

When an input element does not have a Document node as one of its ancestors (i.e. when it is not in the document), it is immutable.

The readonly attribute can also in some cases (e.g. for the Date state, but not the Checkbox state) make an input element immutable.

The form attribute is used to explicitly associate the input element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus.

The indeterminate DOM attribute must initially be set to false. On getting, it must return the last value it was set to. On setting, it must be set to the new value. It has no effect except for changing the appearance of checkbox controls.

The accept, alt, autocomplete, max, min, multiple, pattern, placeholder, required, size, src, step, and type DOM attributes must reflect the respective content attributes of the same name. The maxLength DOM attribute must reflect the maxlength content attribute. The readOnly DOM attribute must reflect the readonly content attribute. The defaultChecked DOM attribute must reflect the checked content attribute. The defaultValue DOM attribute must reflect the value content attribute.

The willValidate, validity, and validationMessage attributes, and the checkValidity() and setCustomValidity() methods, are part of the constraint validation API. The labels attribute provides a list of the element's labels.

4.10.4.1 States of the type attribute

4.10.4.1.1 Hidden state

When an input element's type attribute is in the Hidden state, the rules in this section apply.

The input element represents a value that is not intended to be examined or manipulated by the user.

Constraint validation: If an input element's type attribute is in the Hidden state, it is barred from constraint validation.

If the name attribute is present and has a value that is a case-sensitive match for the string "_charset_", then the element's value attribute must be omitted.

4.10.4.1.2 Text state and Search state

When an input element's type attribute is in the Text state or the Search state, the rules in this section apply.

The input element represents a one line plain text edit control for the element's value.

If the element is mutable, its value should be editable by the user. User agents must not allow users to insert U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters into the element's value.

The value attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

The value sanitization algorithm is as follows: Strip line breaks from the value.

4.10.4.1.3 URL state

When an input element's type attribute is in the URL state, the rules in this section apply.

The input element represents a control for editing a single absolute URL given in the element's value.

If the is mutable, the user agent should allow the user to change the URL represented by its value. User agents may allow the user to set the value to a string that is not a valid absolute URL, but may also or instead automatically escape characters entered by the user so that the value is always a valid absolute URL (even if that isn't the actual value seen and edited by the user in the interface). User agents should allow the user to set the value to the empty string. User agents must not allow users to insert U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters into the value.

The value attribute, if specified, must have a value that is a valid absolute URL.

The value sanitization algorithm is as follows: Strip line breaks from the value.

Constraint validation: While the value of the element is not a valid absolute URL, the element is suffering from a type mismatch.

4.10.4.1.4 E-mail state

When an input element's type attribute is in the E-mail state, the rules in this section apply.

The input element represents a control for editing a list of e-mail addresses given in the element's value.

If the element is mutable, the user agent should allow the user to change the e-mail addresses represented by its value. If the multiple attribute is specified, then the user agent should allow the user to select or provide multiple addresses; otherwise, the user agent should act in a manner consistent with expecting the user to provide a single e-mail address. User agents may allow the user to set the value to a string that is not an valid e-mail address list. User agents should allow the user to set the value to the empty string. User agents must not allow users to insert U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters into the value. User agents may transform the value for display and editing (e.g. converting punycode in the value to IDN in the display and vice versa).

If the multiple attribute is specified on the element, then the value attribute, if specified, must have a value that is a valid e-mail address list; otherwise, the value attribute, if specified, must have a value that is a single valid e-mail address.

The value sanitization algorithm is as follows: Strip line breaks from the value.

Constraint validation: If the multiple attribute is specified on the element, then, while the value of the element is not a valid e-mail address list, the element is suffering from a type mismatch; otherwise, while the value of the element is not a single valid e-mail address, the element is suffering from a type mismatch.

A valid e-mail address list is a set of comma-separated tokens, where each token is itself a valid e-mail address. To obtain the list of tokens from a valid e-mail address list, the user agent must split the string on commas.

A valid e-mail address is a string that matches the production dot-atom "@" dot-atom where dot-atom is defined in RFC 2822 section 3.2.4, excluding the CFWS production everywhere. [RFC2822]

4.10.4.1.5 Password state

When an input element's type attribute is in the Password state, the rules in this section apply.

The input element represents a one line plain text edit control for the element's value. The user agent should obscure the value so that people other than the user cannot see it.

If the element is mutable, its value should be editable by the user. User agents must not allow users to insert U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters into the value.

The value attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

The value sanitization algorithm is as follows: Strip line breaks from the value.

4.10.4.1.6 Date and Time state

When an input element's type attribute is in the Date and Time state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a specific global date and time. User agents may display the date and time in whatever timezone is appropriate for the user.

If the element is mutable, the user agent should allow the user to change the global date and time represented by its value, as obtained by parsing a global date and time from it. User agents must not allow the user to set the value to a string that is not a valid global date and time string expressed in UTC, though user agents may allow the user to set and view the time in another timezone and silently translate the time to and from the UTC timezone in the value. If the user agent provides a user interface for selecting a global date and time, then the value must be set to a valid global date and time string expressed in UTC representing the user's selection. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid global date and time string.

The value sanitization algorithm is as follows: If the value of the element is a valid global date and time string, then adjust the time so that the value represents the same point in time but expressed in the UTC timezone, otherwise, set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid global date and time string. The max attribute, if specified, must have a value that is a valid global date and time string.

The step attribute is expressed in seconds. The step scale factor is 1000 (which converts the seconds to milliseconds, as used in the other algorithms). The default step is 60 seconds.

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest global date and time for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If parsing a global date and time from input results in an error, then return an error; otherwise, return the number of milliseconds elapsed from midnight UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z") to the parsed global date and time, ignoring leap seconds.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid global date and time string expressed in UTC that represents the global date and time that is input milliseconds after midnight UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z").

The algorithm to convert a string to a Date object, given a string input, is as follows: If parsing a global date and time from input results in an error, then return an error; otherwise, return a Date object representing the parsed global date and time, expressed in UTC.

The algorithm to convert a Date object to a string, given a Date object input, is as follows: Return a valid global date and time string expressed in UTC that represents the global date and time that is represented by input.

4.10.4.1.7 Date state

When an input element's type attribute is in the Date state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a specific date.

If the element is mutable, the user agent should allow the user to change the date represented by its value, as obtained by parsing a date from it. User agents must not allow the user to set the value to a string that is not a valid date string. If the user agent provides a user interface for selecting a date, then the value must be set to a valid date string representing the user's selection. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid date string.

The value sanitization algorithm is as follows: If the value of the element is not a valid date string, then set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid date string. The max attribute, if specified, must have a value that is a valid date string.

The step attribute is expressed in days. The step scale factor is 86,400,000 (which converts the days to milliseconds, as used in the other algorithms). The default step is 1 day.

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest date for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If parsing a date from input results in an error, then return an error; otherwise, return the number of milliseconds elapsed from midnight UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z") to midnight UTC on the morning of the parsed date, ignoring leap seconds.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid date string that represents the date that, in UTC, is current input milliseconds after midnight UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z").

The algorithm to convert a string to a Date object, given a string input, is as follows: If parsing a date from input results in an error, then return an error; otherwise, return a Date object representing midnight UTC on the morning of the parsed date.

The algorithm to convert a Date object to a string, given a Date object input, is as follows: Return a valid date string that represents the date current at the time represented by input in the UTC timezone.

4.10.4.1.8 Month state

When an input element's type attribute is in the Month state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a specific month.

If the element is mutable, the user agent should allow the user to change the month represented by its value, as obtained by parsing a month from it. User agents must not allow the user to set the value to a string that is not a valid month string. If the user agent provides a user interface for selecting a month, then the value must be set to a valid month string representing the user's selection. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid month string.

The value sanitization algorithm is as follows: If the value of the element is not a valid month string, then set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid month string. The max attribute, if specified, must have a value that is a valid month string.

The step attribute is expressed in months. The step scale factor is 1 (there is no conversion needed as the algorithms use months). The default step is 1 month.

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest month for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If parsing a month time from input results in an error, then return an error; otherwise, return the number of months between January 1970 and the parsed month.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid month string that represents the month that has input months between it and January 1970.

The algorithm to convert a string to a Date object, given a string input, is as follows: If parsing a month from input results in an error, then return an error; otherwise, return a Date object representing midnight UTC on the morning of the first day of the parsed month.

The algorithm to convert a Date object to a string, given a Date object input, is as follows: Return a valid month string that represents the month current at the time represented by input in the UTC timezone.

4.10.4.1.9 Week state

When an input element's type attribute is in the Week state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a specific week.

If the element is mutable, the user agent should allow the user to change the week represented by its value, as obtained by parsing a week from it. User agents must not allow the user to set the value to a string that is not a valid week string. If the user agent provides a user interface for selecting a week, then the value must be set to a valid week string representing the user's selection. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid week string.

The value sanitization algorithm is as follows: If the value of the element is not a valid week string, then set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid week string. The max attribute, if specified, must have a value that is a valid week string.

The step attribute is expressed in weeks. The step scale factor is 604,800,000 (which converts the weeks to milliseconds, as used in the other algorithms). The default step is 1 week.

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest week for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If parsing a week string from input results in an error, then return an error; otherwise, return the number of milliseconds elapsed from midnight UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z") to midnight UTC on the morning of the Monday of the parsed week, ignoring leap seconds.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid week string that represents the week that, in UTC, is current input milliseconds after midnight UTC on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0Z").

The algorithm to convert a string to a Date object, given a string input, is as follows: If parsing a week from input results in an error, then return an error; otherwise, return a Date object representing midnight UTC on the morning of the Monday of the parsed week.

The algorithm to convert a Date object to a string, given a Date object input, is as follows: Return a valid week string that represents the week current at the time represented by input in the UTC timezone.

4.10.4.1.10 Time state

When an input element's type attribute is in the Time state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a specific time.

If the element is mutable, the user agent should allow the user to change the time represented by its value, as obtained by parsing a time from it. User agents must not allow the user to set the value to a string that is not a valid time string. If the user agent provides a user interface for selecting a time, then the value must be set to a valid time string representing the user's selection. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid time string.

The value sanitization algorithm is as follows: If the value of the element is not a valid time string, then set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid time string. The max attribute, if specified, must have a value that is a valid time string.

The step attribute is expressed in seconds. The step scale factor is 1000 (which converts the seconds to milliseconds, as used in the other algorithms). The default step is 60 seconds.

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest time for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If parsing a time from input results in an error, then return an error; otherwise, return the number of milliseconds elapsed from midnight to the parsed time on a day with no time changes.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid time string that represents the time that is input milliseconds after midnight on a day with no time changes.

The algorithm to convert a string to a Date object, given a string input, is as follows: If parsing a time from input results in an error, then return an error; otherwise, return a Date object representing the parsed time in UTC on 1970-01-01.

The algorithm to convert a Date object to a string, given a Date object input, is as follows: Return a valid time string that represents the UTC time component that is represented by input.

4.10.4.1.11 Local Date and Time state

When an input element's type attribute is in the Local Date and Time state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a local date and time, with no time zone information.

If the element is mutable, the user agent should allow the user to change the date and time represented by its value, as obtained by parsing a date and time from it. User agents must not allow the user to set the value to a string that is not a valid local date and time string. If the user agent provides a user interface for selecting a local date and time, then the value must be set to a valid local date and time string representing the user's selection. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid local date and time string.

The value sanitization algorithm is as follows: If the value of the element is not a valid local date and time string, then set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid local date and time string. The max attribute, if specified, must have a value that is a valid local date and time string.

The step attribute is expressed in seconds. The step scale factor is 1000 (which converts the seconds to milliseconds, as used in the other algorithms). The default step is 60 seconds.

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest local date and time for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If parsing a date and time from input results in an error, then return an error; otherwise, return the number of milliseconds elapsed from midnight on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0") to the parsed local date and time, ignoring leap seconds.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid local date and time string that represents the date and time that is input milliseconds after midnight on the morning of 1970-01-01 (the time represented by the value "1970-01-01T00:00:00.0").

4.10.4.1.12 Number state

When an input element's type attribute is in the Number state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a number.

If the element is mutable, the user agent should allow the user to change the number represented by its value, as obtained from applying the rules for parsing floating point number values to it. User agents must not allow the user to set the value to a string that is not a valid floating point number. If the user agent provides a user interface for selecting a number, then the value must be set to the best representation of the floating point number representing the user's selection. User agents should allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid floating point number.

The value sanitization algorithm is as follows: If the value of the element is not a valid floating point number, then set it to the empty string instead.

The min attribute, if specified, must have a value that is a valid floating point number. The max attribute, if specified, must have a value that is a valid floating point number.

The step scale factor is 1. The default step is 1 (allowing only integers, unless the min attribute has a non-integer value).

When the element is suffering from a step mismatch, the user agent may round the element's value to the nearest number for which the element would not suffer from a step mismatch.

The algorithm to convert a string to a number, given a string input, is as follows: If applying the rules for parsing floating point number values to input results in an error, then return an error; otherwise, return the resulting number.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid floating point number that represents input.

4.10.4.1.13 Range state

When an input element's type attribute is in the Range state, the rules in this section apply.

The input element represents a control for setting the element's value to a string representing a number, but with the caveat that the exact value is not important, letting UAs provide a simpler interface than they do for the Number state.

In this state, the range and step constraints are enforced even during user input, and there is no way to set the value to the empty string.

If the element is mutable, the user agent should allow the user to change the number represented by its value, as obtained from applying the rules for parsing floating point number values to it. User agents must not allow the user to set the value to a string that is not a valid floating point number. If the user agent provides a user interface for selecting a number, then the value must be set to a best representation of the floating point number representing the user's selection. User agents must not allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid floating point number.

The value sanitization algorithm is as follows: If the value of the element is not a valid floating point number, then set it to a valid floating point number that represents the default value.

The min attribute, if specified, must have a value that is a valid floating point number. The default minimum is 0. The max attribute, if specified, must have a value that is a valid floating point number. The default maximum is 100.

The default value is the minimum plus half the difference between the minimum and the maximum, unless the maximum is less than the minimum, in which case the default value is the minimum.

When the element is suffering from a range underflow, the user agent must set the element's value to a valid floating point number that represents the minimum.

When the element is suffering from a range overflow, if the maximum is not less than the minimum, the user agent must set the element's value to a valid floating point number that represents the maximum.

The step scale factor is 1. The default step is 1 (allowing only integers, unless the min attribute has a non-integer value).

When the element is suffering from a step mismatch, the user agent must round the element's value to the nearest number for which the element would not suffer from a step mismatch, and which is greater than or equal to the minimum, and, if the maximum is not less than the minimum, which is less than or equal to the maximum.

The algorithm to convert a string to a number, given a string input, is as follows: If applying the rules for parsing floating point number values to input results in an error, then return an error; otherwise, return the resulting number.

The algorithm to convert a number to a string, given a number input, is as follows: Return a valid floating point number that represents input.

4.10.4.1.14 Color state

When an input element's type attribute is in the Color state, the rules in this section apply.

The input element represents a color well control, for setting the element's value to a string representing a simple color.

In this state, there is always a color picked, and there is no way to set the value to the empty string.

If the element is mutable, the user agent should allow the user to change the color represented by its value, as obtained from applying the rules for parsing simple color values to it. User agents must not allow the user to set the value to a string that is not a valid lowercase simple color. If the user agent provides a user interface for selecting a color, then the value must be set to the result of using the rules for serialising simple color values to the user's selection. User agents must not allow the user to set the value to the empty string.

The value attribute, if specified, must have a value that is a valid simple color.

The value sanitization algorithm is as follows: If the value of the element is a valid simple color, then set it to the value of the element converted to lowercase; otherwise, set it to the string "#000000".

4.10.4.1.15 Checkbox state

When an input element's type attribute is in the Checkbox state, the rules in this section apply.

The input element represents a two-state control that represents the element's checkedness state. If the element's checkedness state is true, the control represents a positive selection, and if it is false, a negative selection. If the element's indeterminate DOM attribute is set to true, then the control's selection should be obscured as if the control was in a third, indeterminate, state.

The control is never a true tri-state control, even if the element's indeterminate DOM attribute is set to true. The indeterminate DOM attribute only gives the appearance of a third state.

If the element is mutable, then: The pre-click activation steps consist of setting the element's checkedness to its opposite value (i.e. true if it is false, false if it is true), and of setting the element's indeterminate DOM attribute to false. The canceled activation steps consist of setting the checkedness and the element's indeterminate DOM attribute back to the values they had before the pre-click activation steps were run. The activation behavior is to fire a simple event called change at the element, then broadcast formchange events at the element's form owner.

Constraint validation: If the element is required and its checkedness is false, then the element is suffering from being missing.

4.10.4.1.16 Radio Button state

When an input element's type attribute is in the Radio Button state, the rules in this section apply.

The input element represents a control that, when used in conjunction with other input elements, forms a radio button group in which only one control can have its checkedness state set to true. If the element's checkedness state is true, the control represents the selected control in the group, and if it is false, it indicates a control in the group that is not selected.

The radio button group that contains an input element a also contains all the other input elements b that fulfill all of the following conditions:

• The input element b's type attribute is in the Radio Button state.
• Either neither a nor b have a form owner, or they both have one and it is the same for both.
• They both have a name attribute, and the value of a's name attribute is a compatibility caseless match for the value of b's name attribute.

A document must not contain an input element whose radio button group contains only that element.

When any of the following events occur, if the element's checkedness state is true after the event, the checkedness state of all the other elements in the same radio button group must be set to false:

• The element's checkedness state is set to true (for whatever reason).
• The element's name attribute is added, removed, or changes value.
• The element's form owner changes.

If the element is mutable, then: The pre-click activation steps consist of setting the element's checkedness to true. The canceled activation steps consist of setting the element's checkedness to false. The activation behavior is to fire a simple event called change at the element, then broadcast formchange events at the element's form owner.

Constraint validation: If the element is required and all of the input elements in the radio button group have a checkedness that is false, then the element is suffering from being missing.

If none of the radio buttons in a radio button group are checked when they are inserted into the document, then they will all be initially unchecked in the interface, until such time as one of them is checked (either by the user or by script).

4.10.4.1.17 File Upload state

When an input element's type attribute is in the File Upload state, the rules in this section apply.

The input element represents a list of selected files, each file consisting of a file name, a file type, and a file body (the contents of the file).

If the element is mutable, the user agent should allow the user to change the files on the list, e.g. adding or removing files. Files can be from the filesystem or created on the fly, e.g. a picture taken from a camera connected to the user's device.

Constraint validation: If the element is required and the list of selected files is empty, then the element is suffering from being missing.

Unless the multiple attribute is set, there must be no more than one file in the list of selected files.

The accept attribute may be specified to provide user agents with a hint of what file types the server will be able to accept.

If specified, the attribute must consist of a set of comma-separated tokens, each of which must be an ASCII case-insensitive match for one of the following:

The string audio/*

Indicates that sound files are accepted.

The string video/*

Indicates that video files are accepted.

The string image/*

Indicates that image files are accepted.

A valid MIME type, with no parameters

Indicates that files of the specified type are accepted. [RFC2046]

The tokens must not be ASCII case-insensitive matches for any of the other tokens (i.e. duplicates are not allowed). To obtain the list of tokens from the attribute, the user agent must split the attribute value on commas.

User agents should prevent the user from selecting files that are not accepted by one (or more) of these tokens.

4.10.4.1.18 Submit Button state

When an input element's type attribute is in the Submit Button state, the rules in this section apply.

The input element represents a button that, when activated, submits the form. If the element has a value attribute, the button's label must be the value of that attribute; otherwise, it must be an implementation-defined string that means "Submit" or some such. The element is a button, specifically a submit button.

If the element is mutable, the user agent should allow the user to activate the element.

The element's activation behavior, if the element has a form owner, is to submit the form owner from the input element; otherwise, it is to do nothing.

The action, enctype, method, novalidate, and target attributes are attributes for form submission.

4.10.4.1.19 Image Button state

When an input element's type attribute is in the Image Button state, the rules in this section apply.

The input element represents either an image from which a user can select a coordinate and submit the form, or alternatively a button from which the user can submit the form. The element is a button, specifically a submit button.

The image is given by the src attribute. The src attribute must be present, and must contain a valid URL referencing a non-interactive, optionally animated, image resource that is neither paged nor scripted.

When any of the following events occur, unless the user agent cannot support images, or its support for images has been disabled, or the user agent only fetches elements on demand, the user agent must resolve the value of the src attribute, relative to the element, and if that is successful, must fetch the resulting absolute URL:

• The input element's type attribute is first set to the Image Button state (possibly when the element is first created), and the src attribute is present.
• The input element's type attribute is changed back to the Image Button state, and the src attribute is present, and its value has changed since the last time the type attribute was in the Image Button state.
• The input element's type attribute is in the Image Button state, and the src attribute is set or changed.

Fetching the image must delay the load event.

If the image was successfully obtained, with no network errors, and the image's type is a supported image type, and the image is a valid image of that type, then the image is said to be available. If this is true before the image is completely downloaded, each task that is queued by the networking task source while the image is being fetched must update the presentation of the image appropriately.

The user agents should apply the image sniffing rules to determine the type of the image, with the image's associated Content-Type headers giving the official type. If these rules are not applied, then the type of the image must be the type given by the image's associated Content-Type headers.

User agents must not support non-image resources with the input element. User agents must not run executable code embedded in the image resource. User agents must only display the first page of a multipage resource. User agents must not allow the resource to act in an interactive fashion, but should honour any animation in the resource.

The task that is queued by the networking task source once the resource has been fetched, must, if the download was successful and the image is available, queue a task to fire a load event on the input element; and otherwise, if the fetching process fails without a response from the remote server, or completes but the image is not a valid or supported image, queue a task to fire an error event on the input element.

The alt attribute provides the textual label for the alternative button for users and user agents who cannot use the image. The alt attribute must also be present, and must contain a non-empty string.

The input element supports dimension attributes.

If the src attribute is set, and the image is available and the user agent is configured to display that image, then: The element represents a control for selecting a coordinate from the image specified by the src attribute; if the element is mutable, the user agent should allow the user to select this coordinate. The activation behavior in this case consists of taking the user's selected coordinate, and then, if the element has a form owner, submitting the input element's form owner from the input element. If the user activates the control without explicitly selecting a coordinate, then the coordinate (0,0) must be assumed.

Otherwise, the element represents a submit button whose label is given by the value of the alt attribute; if the element is mutable, the user agent should allow the user to activate the button. The activation behavior in this case consists of setting the selected coordinate to (0,0), and then, if the element has a form owner, submitting the input element's form owner from the input element.

The selected coordinate must consist of an x-component and a y-component. The x-component must be greater than or equal to zero, and less than or equal to the rendered width, in CSS pixels, of the image, plus the widths of the left and right borders rendered around the image, if any. The y-component must be greater than or equal to zero, and less than or equal to the rendered height, in CSS pixels, of the image, plus the widths of the top and bottom bordered rendered around the image, if any. The coordinates must be relative to the image's borders, where there are any, and the edge of the image otherwise.

The action, enctype, method, novalidate, and target attributes are attributes for form submission.

Many aspects of this state's behavior are similar to the behavior of the img element. Readers are encouraged to read that section, where many of the same requirements are described in more detail.

4.10.4.1.20 Reset Button state

When an input element's type attribute is in the Reset Button state, the rules in this section apply.

The input element represents a button that, when activated, resets the form. If the element has a value attribute, the button's label must be the value of that attribute; otherwise, it must be an implementation-defined string that means "Reset" or some such. The element is a button.

If the element is mutable, the user agent should allow the user to activate the element.

The element's activation behavior, if the element has a form owner, is to reset the form owner; otherwise, it is to do nothing.

Constraint validation: The element is barred from constraint validation.

The value DOM attribute applies to this element and is in mode default.

4.10.4.1.21 Button state

When an input element's type attribute is in the Button state, the rules in this section apply.

The input element represents a button with no default behavior. If the element has a value attribute, the button's label must be the value of that attribute; otherwise, it must be the empty string. The element is a button.

If the element is mutable, the user agent should allow the user to activate the element. The element's activation behavior is to do nothing.

Constraint validation: The element is barred from constraint validation.

The value DOM attribute applies to this element and is in mode default.

4.10.4.2 Common input element attributes

These attributes only apply to an input element if its type attribute is in a state whose definition declares that the attribute applies. When an attribute doesn't apply to an input element, user agents must ignore the attribute.

4.10.4.2.1 The autocomplete attribute

The autocomplete attribute is an enumerated attribute. The attribute has three states. The on keyword maps to the on state, and the off keyword maps to the off state. The attribute may also be omitted. The missing value default is the default state.

The off state indicates that the control's input data is either particularly sensitive (for example the activation code for a nuclear weapon) or is a value that will never be reused (for example a one-time-key for a bank login) and the user will therefore have to explicitly enter the data each time, instead of being able to rely on the UA to prefill the value for him.

Conversely, the on state indicates that the value is not particularly sensitive and the user can expect to be able to rely on his user agent to remember values he has entered for that control.

The default state indicates that the user agent is to use the autocomplete attribute on the element's form owner instead.

Each input element has a resulting autocompletion state, which is either on or off.

When an input element's autocomplete attribute is in the on state, when an input element's autocomplete attribute is in the default state, and the element has no form owner, and when an input element's autocomplete attribute is in the default state, and the element's form owner's autocomplete attribute is in the on state, the input element's resulting autocompletion state is on. Otherwise, the input element's resulting autocompletion state is off.

When an input element's resulting autocompletion state is on, the user agent may store the value entered by the user so that if the user returns to the page, the UA can prefill the form. Otherwise, the user agent should not remember the control's value.

The autocompletion mechanism must be implemented by the user agent acting as if the user had modified the element's value, and must be done at a time where the element is mutable (e.g. just after the element has been inserted into the document, or when the user agent stops parsing).

<p>Account: <input type="text" name="ac" autocomplete="off"></p>
<p>PIN: <input type="text" name="pin" autocomplete="off"></p>

A user agent may allow the user to override the resulting autocompletion state and set it to always on, always allowing values to be remembered and prefilled), or always off, never remembering values. However, the ability to override the resulting autocompletion state to on should not be trivially accessible, as there are significant security implications for the user if all values are always remembered, regardless of the site's preferences.

4.10.4.2.2 The list attribute

The list attribute is used to identify an element that lists predefined options suggested to the user.

If present, its value must be the ID of a datalist element in the same document.

The suggestions source element is the first element in the document in tree order to have an ID equal to the value of the list attribute, if that element is a datalist element. If there is no list attribute, or if there is no element with that ID, or if the first element with that ID is not a datalist element, then there is no suggestions source element.

If there is a suggestions source element, then each option element that is a descendant of the suggestions source element, that is not disabled, and whose value is a string that isn't the empty string and that the user would be allowed to enter as the input element's value, represents a suggestion. Each suggestion has a value and a label.

When the user agent is allowing the user to edit the input element's value, the user agent should offer the suggestions to the user in a manner suitable for the type of control used. The user agent may use the suggestion's label to identify the suggestion if appropriate. If the user selects a suggestion, then the input element's value must be set to the selected suggestion's value, as if the user had written that value himself.

User agents should filter the suggestions to hide suggestions that would cause the element to not satisfy its constraints.

If the list attribute does not apply, there is no suggestions source element.

4.10.4.2.3 The readonly attribute

The readonly attribute is a boolean attribute. When specified, the element is immutable.

Constraint validation: If the readonly attribute is specified on an input element, the element is barred from constraint validation.

4.10.4.2.4 The size attribute

The size attribute gives the number of characters that, in a visual rendering, the user agent is to allow the user to see while editing the element's value.

The size attribute, if specified, must have a value that is a valid non-negative integer greater than zero.

If the attribute is present, then its value must be parsed using the rules for parsing non-negative integers, and if the result is a number greater than zero, then the user agent should ensure that at least that many characters are visible.

The rendering section will define this in more detail.

The size DOM attribute limited to only positive non-zero numbers.

4.10.4.2.5 The required attribute

The required attribute is a boolean attribute. When specified, the element is required.

Constraint validation: If the element is required, and its value DOM attribute applies and is in the mode value, and the element is mutable, and the element's value is the empty string, then the element is suffering from being missing.

4.10.4.2.6 The multiple attribute

The multiple attribute is a boolean attribute that indicates whether the user is to be allowed to specify more than one value.

4.10.4.2.7 The maxlength attribute

The maxlength attribute, when it applies, is a form control maxlength attribute controlled by the input element's dirty value flag.

If the input element has a maximum allowed value length, then the codepoint length of the value of the element's value attribute must be equal to or less than the element's maximum allowed value length.

4.10.4.2.8 The pattern attribute

The pattern attribute specifies a regular expression against which the control's value is to be checked.

If specified, the attribute's value must match the Pattern production of ECMA 262's grammar. [ECMA262]

Constraint validation: If the element's value is not the empty string, and the element's pattern attribute is specified and the attribute's value, when compiled as an ECMA 262 regular expression with the global, ignoreCase, and multiline flags disabled (see ECMA 262, sections 15.10.7.2 through 15.10.7.4), compiles successfully but the resulting regular expression does not match the entirety of the element's value, then the element is suffering from a pattern mismatch. [ECMA262]

This implies that the regular expression language used for this attribute is the same as that defined in ECMA 262, except that the pattern attribute must match the entire value, not just any subset (somewhat as if it implied a ^(?: at the start of the pattern and a )$ at the end).

When an input element has a pattern attribute specified, authors should include a title attribute to give a description of the pattern. User agents may use the contents of this attribute, if it is present, when informing the user that the pattern is not matched, or at any other suitable time, such as in a tooltip or read out by assistive technology when the control gains focus.

<label> Part number:
 <input pattern="[0-9][A-Z]{3}" name="part"
        title="A part number is a digit followed by three uppercase letters."/>
</label>

 part number is a digit followed by three uppercase letters.
You cannot complete this form until the field is correct.

When a control has a pattern attribute, the title attribute, if used, must describe the pattern. Additional information could also be included, so long as it assists the user in filling in the control. Otherwise, assistive technology would be impaired.

For instance, if the title attribute contained the caption of the control, assistive technology could end up saying something like The text you have entered does not match the required pattern. Birthday, which is not useful.

UAs may still show the title in non-error situations (for example, as a tooltip when hovering over the control), so authors should be careful not to word titles as if an error has necessarily occurred.

4.10.4.2.9 The min and max attributes

The min and max attributes indicate the allowed range of values for the element.

Their syntax is defined by the section that defines the type attribute's current state.

If the element has a min attribute, and the result of applying the algorithm to convert a string to a number to the value of the min attribute is a a number, then that number is the element's minimum; otherwise, if the the type attribute's current state defines a default minimum, then that is the minimum; otherwise, the element has no minimum.)

Constraint validation: When the element has a minimum, and the result of applying the algorithm to convert a string to a number to the string given by the element's value is a number, and the number obtained from that algorithm is less than the minimum, the element is suffering from an underflow.

The min attribute also defines the step base.

If the element has a max attribute, and the result of applying the algorithm to convert a string to a number to the value of the max attribute is a a number, then that number is the element's maximum; otherwise, if the the type attribute's current state defines a default maximum, then that is the maximum; otherwise, the element has no maximum.)

Constraint validation: When the element has a maximum, and the result of applying the algorithm to convert a string to a number to the string given by the element's value is a number, and the number obtained from that algorithm is more than the maximum, the element is suffering from an overflow.

The max attribute's value (the maximum) must not be less than the min attribute's value (its minimum).

If an element has a maximum that is less than its minimum, then so long as the element has a value, it will either be suffering from an underflow or suffering from an overflow.

4.10.4.2.10 The step attribute

The step attribute indicates the granularity that is expected (and required) of the value, by limiting the allowed values. The section that defines the type attribute's current state also defines the default step and the step scale factor, which are used in processing the attribute as described below.

The step attribute, if specified, must either have a value that is a valid floating point number that parses to a number that is greater than zero, or must have a value that is an ASCII case-insensitive match for the string "any".

The attribute provides the allowed value step for the element, as follows:

1. If the attribute is absent, then the allowed value step is the default step multiplied by the step scale factor.
2. Otherwise, if the attribute's value is an ASCII case-insensitive match for the string "any", then there is no allowed value step.
3. Otherwise, if the rules for parsing floating point number values, when they are applied to the attribute's value, return an error, zero, or a number less than zero, then the allowed value step is the default step multiplied by the step scale factor.
4. Otherwise, the allowed value step is the number returned by the rules for parsing floating point number values when they are applied to the attribute's value, multiplied by the step scale factor.

The step base is the result of applying the algorithm to convert a string to a number to the value of the min attribute, unless the element does not have a min attribute specified or the result of applying that algorithm is an error, in which case the step base is zero.

Constraint validation: When the element has an allowed value step, and the result of applying the algorithm to convert a string to a number to the string given by the element's value is a number, and that number subtracted from the step base is not an integral multiple of the allowed value step, the element is suffering from a step mismatch.

4.10.4.2.11 The placeholder attribute

The placeholder attribute represents a short hint (a word or short phrase) intended to aid the user with data entry. A hint could be a sample value or a brief description of the expected format. The attribute, if specified, must have a value that contains no U+000A LINE FEED (LF) or U+000D CARRIAGE RETURN (CR) characters.

For a longer hint or other advisory text, the title attribute is more appropriate.

The placeholder attribute should not be used as an alternative to a label.

User agents should present this hint to the user, after having stripped line breaks from it, when the element's value is the empty string and the control is not focused (e.g. by displaying it inside a blank unfocused control).

<fieldset>
 <legend>Mail Account</legend>
 <p><label>Name: <input type="text" name="fullname" placeholder="John Ratzenberger"></label></p>
 <p><label>Address: <input type="email" name="address" placeholder="john@example.net"></label></p>
 <p><label>Password: <input type="password" name="password"></label></p>
 <p><label>Description: <input type="text" name="desc" placeholder="My Email Account"></label></p>
</fieldset>

4.10.4.3 Common input element APIs

The value DOM attribute allows scripts to manipulate the value of an input element. If the attribute applies, then it is in one of the following modes, which define its behavior:

value

On getting, it must return the current value of the element. On setting, it must set the element's value to the new value, set the element's dirty value flag to true, and then invoke the value sanitization algorithm, if the element's type attribute's current state defines one.

default

On getting, if the element has a value attribute, it must return that attribute's value; otherwise, it must return the empty string. On setting, it must set the element's value attribute to the new value.

default/on

On getting, if the element has a value attribute, it must return that attribute's value; otherwise, it must return the string "on". On setting, it must set the element's value attribute to the new value.

If the attribute does not apply, then on getting and setting it must throw an INVALID_ACCESS_ERR exception.

The checked DOM attribute allows scripts to manipulate the checkedness of an input element. On getting, it must return the current checkedness of the element; and on setting, it must set the element's checkedness to the new value and set the element's dirty checkedness flag to true.

The valueAsDate DOM attribute represents the value of the element, interpreted as a date.

On getting, if the valueAsDate attribute does not apply, as defined for the input element's type attribute's current state, then return null. Otherwise, run the algorithm to convert a string to a Date object defined for that state; if the algorithm returned a Date object, then return it, otherwise, return null.

On setting, if the valueAsDate attribute does not apply, as defined for the input element's type attribute's current state, then throw an INVALID_ACCESS_ERR exception; otherwise, if the new value is null, then set the value of the element to the empty string; otherwise, run the algorithm to convert a Date object to a string, as defined for that state, on the new value, and set the value of the element to resulting string.

The valueAsNumber DOM attribute represents the value of the element, interpreted as a number.

On getting, if the valueAsNumber attribute does not apply, as defined for the input element's type attribute's current state, then return a Not-a-Number (NaN) value. Otherwise, if the valueAsDate attribute applies, run the algorithm to convert a string to a Date object defined for that state; if the algorithm returned a Date object, then return the time value of the object (the number of milliseconds from midnight UTC the morning of 1970-01-01 to the time represented by the Date object), otherwise, return a Not-a-Number (NaN) value. Otherwise, run the algorithm to convert a string to a number defined for that state; if the algorithm returned a number, then return it, otherwise, return a Not-a-Number (NaN) value.

On setting, if the valueAsNumber attribute does not apply, as defined for the input element's type attribute's current state, then throw an INVALID_ACCESS_ERR exception. Otherwise, if the valueAsDate attribute applies, run the algorithm to convert a Date object to a string defined for that state, passing it a Date object whose time value is the new value, and set the value of the element to resulting string. Otherwise, run the algorithm to convert a number to a string, as defined for that state, on the new value, and set the value of the element to resulting string.

The stepDown() and stepUp() methods, when invoked, must run the following algorithm:

1. If the stepDown() and stepUp() methods do not apply, as defined for the input element's type attribute's current state, then throw an INVALID_ACCESS_ERR exception, and abort these steps.

2. If the element has no allowed value step, then throw an INVALID_ACCESS_ERR exception, and abort these steps.

3. If applying the algorithm to convert a string to a number to the string given by the element's value results in an error, then throw an INVALID_ACCESS_ERR exception, and abort these steps; otherwise, let value be the result of that algorithm.

4. If the method invoked was the stepDown() method, negate value.

5. Let value be the result of adding the allowed value step to value.

6. Let value as string be the result of running the algorithm to convert a number to a string, as defined for the input element's type attribute's current state, on value.

7. If the element has a minimum, and the value is less than that minimum, then throw a INVALID_ACCESS_ERR exception.

8. If the element has a maximum, and the value is greater than that maximum, then throw a INVALID_ACCESS_ERR exception.

9. Set the value of the element to value as string.

The list DOM attribute must return the current suggestions source element, if any, or null otherwise.

The selectedOption DOM attribute must return the first option element, in tree order, to be a child of the suggestions source element and whose value matches the input element's value, if any. If there is no suggestions source element, or if it contains no matching option element, then the selectedOption attribute must return null.

4.10.4.4 Common event behaviors

When the input event applies, any time the user causes the element's value to change, the user agent must queue a task to fire a simple event called input at the input element, then broadcast forminput events at the input element's form owner. User agents may wait for a suitable break in the user's interaction before queuing the task; for example, a user agent could wait for the user to have not hit a key for 100ms, so as to only fire the event when the user pauses, instead of continuously for each keystroke.

Examples of a user changing the element's value would include the user typing into a text field, pasting a new value into the field, or undoing an edit in that field. Some user interactions do not cause changes to the value, e.g. hitting the "delete" key in an empty text field, or replacing some text in the field with text from the clipboard that happens to be exactly the same text.

When the change event applies, if the element does not have an activation behavior defined but uses a user interface that involves an explicit commit action, then any time the user commits a change to the element's value or list of selected files, the user agent must queue a task to fire a simple event called change at the input element, then broadcast formchange events at the input element's form owner.

An example of a user interface with a commit action would be a File Upload control that consists of a single button that brings up a file selection dialog: when the dialog is closed, if that the file selection changed as a result, then the user has commited a new file selection.

Another example of a user interface with a commit action would be a Date control that allows both text-based user input and user selection from a drop-down calendar: while text input might not have an explicit commit step, selecting a date from the drop down calendar and then dismissing the drop down would be a commit action.

When the user agent changes the element's value on behalf of the user (e.g. as part of a form prefilling feature), the user agent must follow these steps:

1. If the input event applies, queue a task to fire a simple event called input at the input element.
2. If the input event applies, broadcast forminput events at the input element's form owner.
3. If the change event applies, queue a task to fire a simple event called change at the input element.
4. If the change event applies, broadcast formchange events at the input element's form owner.

In addition, when the change event applies, change events can also be fired as part of the element's activation behavior and as part of the unfocusing steps.

The task source for these task is the user interaction task source.

4.10.5 The button element

Categories

Flow content.

Phrasing content.

Interactive content.

Listed, labelable, and submittable form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Phrasing content, but there must be no interactive content descendant.

Content attributes:

Global attributes

action

autofocus

disabled

enctype

form

method

name

novalidate

target

type

value

DOM interface:

interface HTMLButtonElement : HTMLElement {
           attribute DOMString action;
           attribute boolean autofocus;
           attribute boolean disabled;
           attribute DOMString enctype;
  readonly attribute HTMLFormElement form;
           attribute DOMString method;
           attribute DOMString name;
           attribute DOMString noValidate;
           attribute DOMString target;
           attribute DOMString type;
           attribute DOMString value;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;
};

The button element represents a button. If the element is not disabled, then the user agent should allow the user to activate the button.

The element is a button.

The type attribute controls the behavior of the button when it is activated. It is an enumerated attribute. The following table lists the keywords and states for the attribute — the keywords in the left column map to the states in the cell in the second column on the same row as the keyword.

The missing value default is the Submit Button state.

If the type attribute is in the Submit Button state, the element is specifically a submit button.

If the element is not disabled, the activation behavior of the button element is to run the steps defined in the following list for the current state of the element's type attribute.

Submit Button

If the element has a form owner, the element must submit the form owner from the button element.

Reset Button

If the element has a form owner, the element must reset the form owner.

Button

Do nothing.

The form attribute is used to explicitly associate the button element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus. The action, enctype, method, novalidate, and target attributes are attributes for form submission.

The value attribute gives the element's value for the purposes of form submission. The value attribute must not be present unless the form attribute is present. The element's value is the value of the element's value attribute, if there is one, or the empty string otherwise.

A button (and its value) is only included in the form submission if the button itself was used to initiate the form submission.

The value and type DOM attributes must reflect the respective content attributes of the same name.

The willValidate, validity, and validationMessage attributes, and the checkValidity() and setCustomValidity() methods, are part of the constraint validation API. The labels attribute provides a list of the element's labels.

4.10.6 The select element

Categories

Flow content.

Phrasing content.

Interactive content.

Listed, labelable, submittable, and resettable form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Zero or more option or optgroup elements.

Content attributes:

Global attributes

autofocus

disabled

form

multiple

name

size

DOM interface:

[Callable=namedItem]
interface HTMLSelectElement : HTMLElement {
           attribute boolean autofocus;
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute boolean multiple;
           attribute DOMString name;
           attribute boolean size;

  readonly attribute DOMString type;

  readonly attribute HTMLOptionsCollection options;
           attribute unsigned long length;
  [IndexGetter] any item(in DOMString name);
  [NameGetter] any namedItem(in DOMString name);
  void add(in HTMLElement element, in HTMLElement before);
  void add(in HTMLElement element, in long before);
  void remove(in long index);

  readonly attribute HTMLCollection selectedOptions;
           attribute long selectedIndex;
           attribute DOMString value;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;
};

The select element represents a control for selecting amongst a set of options.

The multiple attribute is a boolean attribute. If the attribute is present, then the select element represents a control for selecting zero or more options from the list of options. If the attribute is absent, then the select element represents a control for selecting a single option from the list of options.

The list of options for a select element consists of all the option element children of the select element, and all the option element children of all the optgroup element children of the select element, in tree order.

The size attribute gives the number of options to show to the user. The size attribute, if specified, must have a value that is a valid non-negative integer greater than zero. If the multiple attribute is present, then the size attribute's default value is 4. If the multiple attribute is absent, then the size attribute's default value is 1.

If the multiple attribute is absent, and the element is not disabled, then the user agent should allow the user to pick an option element in its list of options that is itself not disabled. Upon this option element being picked (either through a click, or through unfocusing the element after changing its value, or through a menu command, or through any other mechanism), and before the relevant user interaction event is queued (e.g. before the click event), the user agent must set the selectedness of the picked option element to true and then queue a task to fire a simple event called change at the select element, using the user interaction task source as the task source, then broadcast formchange events at the element's form owner.

If the multiple attribute is absent, whenever an option element in the select element's list of options has its selectedness set to true, and whenever an option element with its selectedness set to true is added to the select element's list of options, the user agent must set the selectedness of all the other option element in its list of options to false.

If the multiple attribute is absent, whenever there are no option elements in the select element's list of options that have their selectedness set to true, the user agent must set the selectedness of the first option element in the list of options in tree order that is not disabled, if any, to true.

If the multiple attribute is present, and the element is not disabled, then the user agent should allow the user to toggle the selectedness of the option elements in its list of options that are themselves not disabled (either through a click, or through a menu command, or any other mechanism). Upon the selectedness of one or more option elements being changed by the user, and before the relevant user interaction event is queued (e.g. before a related click event), the user agent must queue a task to fire a simple event called change at the select element, using the user interaction task source as the task source, then broadcast formchange events at the element's form owner.

The reset algorithm for select elements is to go through all the option elements in the element's list of options, and set their selectedness to true if the option element has a selected attribute, and false otherwise.

The form attribute is used to explicitly associate the select element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus.

The type DOM attribute, on getting, must return the string "select-one" if the multiple attribute is absent, and the string "select-multiple" if the multiple attribute is present.

The options DOM attribute must return an HTMLOptionsCollection rooted at the select node, whose filter matches the elements in the list of options.

The options collection is also mirrored on the HTMLSelectElement object. The length DOM attribute must return the number of nodes represented by the options collection. The indices of the supported indexed properties at any instant are the indicies supported by the object returned by the options attribute at that instant. The names of the supported named properties at any instant are the names supported by the object returned by the options attribute at that instant.

The item(index) method must return the value returned by the method of the same name on the options collection, when invoked with the same argument.

The namedItem(name) method must return the value returned by the method of the same name on the options collection, when invoked with the same argument.

Similarly, the add() and remove() methods must act like their namesake methods on that same options collection.

The selectedOptions DOM attribute must return an HTMLCollection rooted at the select node, whose filter matches the elements in the list of options that have their selectedness set to true.

The selectedIndex DOM attribute, on getting, must return the index of the first option element in the list of options in tree order that has its selectedness set to true, if any. If there isn't one, then it must return -1.

On setting, the selectedIndex attribute must set the selectedness of all the option elements in the list of options to false, and then the option element in the list of options whose index is the given new value, if any, must have its selectedness set to true.

The value DOM attribute, on getting, must return the value of the first option element in the list of options in tree order that has its selectedness set to true, if any. If there isn't one, then it must return the empty string.

On setting, the value attribute must set the selectedness of all the option elements in the list of options to false, and then first the option element in the list of options, in tree order, whose value is equal to the given new value, if any, must have its selectedness set to true.

The multiple and size DOM attributes must reflect the respective content attributes of the same name. The size DOM attribute limited to only positive non-zero numbers.

The willValidate, validity, and validationMessage attributes, and the checkValidity() and setCustomValidity() methods, are part of the constraint validation API. The labels attribute provides a list of the element's labels.

4.10.7 The datalist element

Categories

Flow content.

Phrasing content.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Either: phrasing content.

Or: Zero or more option elements.

Content attributes:

Global attributes

DOM interface:

interface HTMLDataListElement : HTMLElement {
  readonly attribute HTMLCollection options;
};

The datalist element represents a set of option elements that represent predefined options for other controls. The contents of the element represents fallback content for legacy user agents, intermixed with option elements that represent the predefined options. In the rendering, the datalist element represents nothing and it, along with its children, should be hidden.

The datalist element is hooked up to an input element using the list attribute on the input element.

The options DOM attribute must return an HTMLCollection rooted at the datalist node, whose filter matches option elements.

Constraint validation: If an element has a datalist element ancestor, it is barred from constraint validation.

4.10.8 The optgroup element

Categories

None.

Contexts in which this element may be used:

As a child of a select element.

Content model:

Zero or more option elements.

Content attributes:

Global attributes

disabled

label

DOM interface:

interface HTMLOptGroupElement : HTMLElement {
           attribute boolean disabled;
           attribute DOMString label;
};

The optgroup element represents a group of option elements with a common label.

The element's group of option elements consists of the option elements that are children of the optgroup element.

When showing option elements in select elements, user agents should show the option elements of such groups as being related to each other and separate from other option elements.

The disabled attribute is a boolean attribute and can be used to disable a group of option elements together.

The label attribute must be specified. Its value gives the name of the group, for the purposes of the user interface. User agents should use this attribute's value when labelling the group of option elements in a select element.

The disabled and label attributes must reflect the respective content attributes of the same name.

4.10.9 The option element

Categories

None.

Contexts in which this element may be used:

As a child of a select element.

As a child of a datalist element.

As a child of an optgroup element.

Content model:

Text.

Content attributes:

Global attributes

disabled

label

selected

value

DOM interface:

[NamedConstructor=Option(),
 NamedConstructor=Option(in DOMString text),
 NamedConstructor=Option(in DOMString text, in DOMString value),
 NamedConstructor=Option(in DOMString text, in DOMString value, in boolean defaultSelected),
 NamedConstructor=Option(in DOMString text, in DOMString value, in boolean defaultSelected, in boolean selected)]
interface HTMLOptionElement : HTMLElement {
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute DOMString label;
           attribute boolean defaultSelected;
           attribute boolean selected;
           attribute DOMString value;

  readonly attribute DOMString text;
  readonly attribute long index;
};

The option element represents an option in a select element or as part of a list of suggestions in a datalist element.

The disabled attribute is a boolean attribute. An option element is disabled if its disabled attribute is present or if it is a child of an optgroup element whose disabled attribute is present.

An option element that is disabled must prevent any click events that are queued on the user interaction task source from being dispatched on the element.

The label attribute provides a label for element. The label of an option element is the value of the label attribute, if there is one, or the textContent of the element, if there isn't.

The value attribute provides a value for element. The value of an option element is the value of the value attribute, if there is one, or the textContent of the element, if there isn't.

The selected attribute represents the default selectedness of the element.

The selectedness of an option element is a boolean state, initially false. If the element is disabled, then the element's selectedness is always false and cannot be set to true. Unless othewise specified, when the element is created, its selectedness must be set to true if the element has a selected attribute. Whenever an option element's selected attribute is added, its selectedness must be set to true.

The Option() constructor with two or more arguments overrides the initial state of the selectedness state to always be false even if the third argument is true (implying that a selected attribute is to be set).

An option element's index is the number of option element that are in the same list of options but that come before it in tree order. If the option element is not in a list of options, then the option element's index is zero.

The disabled, label, and value DOM attributes must reflect the respective content attributes of the same name. The defaultSelected DOM attribute must reflect the selected content attribute.

The selected DOM attribute must return true if the element's selectedness is true, and false otherwise.

The index DOM attribute must return the element's index.

The text DOM attribute must return the same value as the textContent DOM attribute on the element.

The form DOM attribute's behavior depends on whether the option element is in a select element or not. If the option has a select element as its parent, or has a colgroup element as its parent and that colgroup element has a select element as its parent, then the form DOM attribute must return the same value as the form DOM attribute on that select element. Otherwise, it must return null.

Several constructors are provided for creating HTMLOptionElement objects (in addition to the factory methods from DOM Core such as createElement()): Option(), Option(text), Option(text, value), Option(text, value, defaultSelected), and Option(text, value, defaultSelected, selected). When invoked as constructors, these must return a new HTMLOptionElement object (a new option element). If the text argument is present, the new object must have a text node with the value of that argument as its data as its only child. If the value argument is present, the new object must have a value attribute set with the value of the argument as its value. If the defaultSelected argument is present and true, the new object must have a selected attribute set with no value. If the selected argument is present and true, the new object must have its selectedness set to true; otherwise the fouth argument is absent or false, and the selectedness must be set to false, even if the defaultSelected argument is present and true.

4.10.10 The textarea element

Categories

Flow content.

Phrasing content.

Interactive content.

Listed, labelable, submittable, and resettable form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Text.

Content attributes:

Global attributes

autofocus

cols

disabled

form

maxlength

name

readonly

required

rows

wrap

DOM interface:

interface HTMLTextAreaElement : HTMLElement {
           attribute boolean autofocus;
           attribute unsigned long cols;
           attribute boolean disabled;
  readonly attribute HTMLFormElement form;
           attribute long maxLength;
           attribute DOMString name;
           attribute boolean readOnly;
           attribute boolean required;
           attribute unsigned long rows;
           attribute DOMString wrap;

  readonly attribute DOMString type;
           attribute DOMString defaultValue;
           attribute DOMString value;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);

  readonly attribute NodeList labels;
};

The textarea element represents a multiline plain text edit control for the element's raw value. The contents of the control represent the control's default value.

The raw value of a textarea control must be initially the empty string.

The readonly attribute is a boolean attribute used to control whether the text can be edited by the user or not.

Constraint validation: If the readonly attribute is specified on a textarea element, the element is barred from constraint validation.

A textarea element is mutable if it is neither disabled nor has a readonly attribute specified.

When a textarea is mutable, its raw value should be editable by the user. Any time the user causes the element's raw value to change, the user agent must queue a task to fire a simple event called input at the textarea element, then broadcast forminput events at the textarea element's form owner. User agents may wait for a suitable break in the user's interaction before queuing the task; for example, a user agent could wait for the user to have not hit a key for 100ms, so as to only fire the event when the user pauses, instead of continuously for each keystroke.

A textarea element has a dirty value flag, which must be initially set to false, and must be set to true whenever the user interacts with the control in a way that changes the raw value.

When the textarea element's textContent DOM attribute changes value, if the element's dirty value flag is false, then the element's raw value must be set to the value of the element's textContent DOM attribute.

The reset algorithm for textarea elements is to set the element's value to the value of the element's textContent DOM attribute.

The cols attribute specifies the expected maximum number of characters per line. If the cols attribute is specified, its value must be a valid non-negative integer greater than zero. If applying the rules for parsing non-negative integers to the attribute's value results in a number greater than zero, then the element's character width is that value; otherwise, it is 20.

The user agent may use the textarea element's character width as a hint to the user as to how many characters the server prefers per line (e.g. for visual user agents by making the width of the control be that many characters). In visual renderings, the user agent should wrap the user's input in the rendering so that each line is no wider than this number of characters.

The rows attribute specifies the number of lines to show. If the rows attribute is specified, its value must be a valid non-negative integer greater than zero. If applying the rules for parsing non-negative integers to the attribute's value results in a number greater than zero, then the element's character height is that value; otherwise, it is 2.

Visual user agents should set the height of the control to the number of lines given by character height.

The wrap attribute is an enumerated attribute with two keywords and states: the soft keyword which maps to the Soft state, and the the hard keyword which maps to the Hard state. The missing value default is the Soft state.

If the element's wrap attribute is in the Hard state, the cols attribute must be specified.

The element's value is defined to be the element's raw value with the following transformation applied:

1. Replace every occurance of a U+000D CARRIAGE RETURN (CR) character not followed by a U+000A LINE FEED (LF) character, and every occurance of a U+000A LINE FEED (LF) character not proceeded by a U+000D CARRIAGE RETURN (CR) character, by a two-character string consisting of a U+000D CARRIAGE RETURN - U+000A LINE FEED (CRLF) character pair.

2. If the element's wrap attribute is in the Hard state, insert U+000D CARRIAGE RETURN - U+000A LINE FEED (CRLF) character pairs into the string using a UA-defined algorithm so that each line so that each line has no more than character width characters. The the purposes of this requirement, lines are delimited by the start of the string, the end of the string, and U+000D CARRIAGE RETURN - U+000A LINE FEED (CRLF) character pairs.

The maxlength attribute is a form control maxlength attribute controlled by the textarea element's dirty value flag.

If the textarea element has a maximum allowed value length, then the element's children must be such that the codepoint length of the value of the element's textContent DOM attribute is equal to or less than the element's maximum allowed value length.

The required attribute is a boolean attribute.

Constraint validation: If the element has its required attribute specified, and the element is mutable, and the element's value is the empty string, then the element is suffering from being missing.

The form attribute is used to explicitly associate the textarea element with its form owner. The name attribute represents the element's name. The disabled attribute is used to make the control non-interactive and to prevent its value from being submitted. The autofocus attribute controls focus.

The cols, required, rows, and wrap attributes must reflect the respective content attributes of the same name. The cols and rows attributes are limited to only positive non-zero numbers. The maxLength DOM attribute must reflect the maxlength content attribute. The readOnly DOM attribute must reflect the readonly content attribute.

The type DOM attribute must return the value "textarea".

The defaultValue DOM attribute must act like the element's textContent DOM attribute.

The value attribute must, on getting, return the element's raw value; on setting, it must set the element's raw value to the new value.

The willValidate, validity, and validationMessage attributes, and the checkValidity() and setCustomValidity() methods, are part of the constraint validation API. The labels attribute provides a list of the element's labels.

4.10.11 The output element

Categories

Flow content.

Phrasing content.

Listed and resettable form-associated element.

Contexts in which this element may be used:

Where phrasing content is expected.

Content model:

Phrasing content.

Content attributes:

Global attributes

for

form

name

DOM interface:

interface HTMLOutputElement : HTMLElement {
           attribute DOMString htmlFor;
  readonly attribute HTMLFormElement form;
           attribute DOMString name;

  readonly attribute DOMString type;
           attribute DOMString defaultValue;
           attribute DOMString value;

  readonly attribute boolean willValidate;
  readonly attribute ValidityState validity;
  readonly attribute DOMString validationMessage;
  boolean checkValidity();
  void setCustomValidity(in DOMString error);
};

The output element represents the result of a calculation.

The for content attribute allows an explicit relationship to be made between the result of a calculation and the elements that represent the values that went into the calculation or that otherwise influenced the calculation. The for attribute, if specified, must contain a string consisting of an unordered set of unique space-separated tokens, each of which must have the value of an ID of an element in the same Document.

The form attribute is used to explicitly associate the output element with its form owner. The name attribute represents the element's name.

The element has a value mode flag which is either value or default. Initially the value mode flag must be set to default.

When the to value mode flag is in mode default, the contents of the element represent both the value of the element and its default value. When the value mode flag is in mode value, the contents of the element represent the value of the element only, and the default value is only accessible using the defaultValue DOM attribute.

The element also has a default value. Initially, the default value must be the empty string.

Whenever the element's descendants are changed in any way, if the value mode flag is in mode default, the element's default value must be set to the value of the element's textContent DOM attribute.

The reset algorithm for textarea elements is to set the element's textContent DOM attribute to the value of the element's defaultValue DOM attribute (thus replacing the element's child nodes), and then to set the element's value mode flag to default.

The value DOM attribute must act like the element's textContent DOM attribute, except that on setting, in addition, before the child nodes are changed, the element's value mode flag must be set to value.

The defaultValue DOM attribute, on getting, must return the element's default value. On setting, the attribute must set the element's default value, and, if the element's value mode flag is in the mode default, set the element's textContent DOM attribute as well.

The type attribute must return the string "output".

The htmlFor DOM attribute must reflect the for content attribute.

The willValidate, validity, and validationMessage attributes, and the checkValidity() and setCustomValidity() methods, are part of the constraint validation API.

Constraint validation: output elements are always barred from constraint validation.

4.10.12 Association of controls and forms

A form-associated element can have a relationship with a form element, which is called the element's form owner. If a form-associated element is not associated with a form element, its form owner is said to be null.

A form-associated element is, by default, associated with its nearest ancestor form element (as described below), but may have a form attribute specified to override this.

If a form-associated element has a form attribute specified, then its value must be the ID of a form element in the element's owner Document.

When a form-associated element is created, its form owner must be initialized to null (no owner).

When a form-associated element is to be associated with a form, its form owner must be set to that form.

When a form-associated element's ancestor chain changes, e.g. because it or one of its ancestors was inserted or removed from a Document, then the user agent must reset the form owner of that element.

When a form-associated element's form attribute is added, removed, or has its value changed, then the user agent must reset the form owner of that element.

When a form-associated element has a form attribute and the ID of any of the form elements in the Document changes, then the user agent must reset the form owner of that form-associated element.

When the user agent is to reset the form owner of a form-associated element, it must run the following steps:

1. If the element's form owner is not null, and the element's form content attribute is not present, and the element's form owner is one of the ancestors of the element after the change to the ancestor chain, then do nothing, and abort these steps.

2. Let the element's form owner be null.

3. If the element has a form content attribute, then run these substeps:

   1. If the first element in the Document to have an ID that is equal to the element's form content attribute's value is a form element, then associate the form-associated element with that form element.

   2. Abort the "reset the form owner" steps.

4. Otherwise, if the form-associated element in question has an ancestor form element, then associate the form-associated element with the nearest such ancestor form element.

5. Otherwise, the element is left unassociated.

Form-associated elements have a form DOM attribute, which, on getting, must return the element's form owner, or null if there isn't one.

Constraint validation: If an element has no form owner, it is barred from constraint validation.

4.10.13 Attributes common to form controls

4.10.13.1 Naming form controls

The name content attribute gives the name of the form control, as used in form submission and in the form element's elements object. If the attribute is specified, its value must not be the empty string.

Constraint validation: If an element does not have a name attribute specified, or its name attribute's value is the empty string, then it is barred from constraint validation.

The name DOM attribute must reflect the name content attribute.

4.10.13.2 Enabling and disabling form controls

The disabled content attribute is a boolean attribute.

A form control is disabled if its disabled attribute is set, or if it is a descendant of a fieldset element whose disabled attribute is set.

A form control that is disabled must prevent any click events that are queued on the user interaction task source from being dispatched on the element.

Constraint validation: If an element is disabled, it is barred from constraint validation.

The disabled DOM attribute must reflect the disabled content attribute.

4.10.13.3 A form control's value

Form controls have a value and a checkedness. (The latter is only used by input elements.) These are used to describe how the user interacts with the control.

4.10.13.4 Autofocusing a form control

The autofocus content attribute allows the user to indicate that a control is to be focused as soon as the page is loaded, allowing the user to just start typing without having to manually focus the main control.

The autofocus attribute is a boolean attribute.

There must not be more than one element in the document with the autofocus attribute specified.

Whenever an element with the autofocus attribute specified is inserted into a document, the user agent should queue a task that checks to see if the element is focusable, and if so, runs the focusing steps for that element. User agents may also change the scrolling position of the document, or perform some other action that brings the element to the user's attention. The task source for this task is the DOM manipulation task source.

User agents may ignore this attribute if the user has indicated (for example, by starting to type in a form control) that he does not wish focus to be changed.

Focusing the control does not imply that the user agent must focus the browser window if it has lost focus.

The autofocus DOM attribute must reflect the content attribute of the same name.

<input maxlength="256" name="q" value="" autofocus>
<input type="submit" value="Search">

4.10.13.5 Limiting user input length

A form control maxlength attribute, controlled by a dirty value flag declares a limit on the number of characters a user can input.

If an element has its form control maxlength attribute specified, the attribute's value must be a valid non-negative integer. If the attribute is specified and applying the rules for parsing non-negative integers to its value results in a number, then that number is the element's maximum allowed value length. If the attribute is omitted or parsing its value results in an error, then there is no maximum allowed value length.

Constraint validation: If an element has a maximum allowed value length, and its dirty value flag is false, and the codepoint length of the element's value is greater than the element's maximum allowed value length, then the element is suffering from being too long.

User agents may prevent the user from causing the element's value to be set to a value whose codepoint length is greater than the element's maximum allowed value length.

4.10.13.6 Form submission

Attributes for form submission can be specified both on form elements and on elements that represent buttons that submit forms, e.g. an input element whose type attribute is in the Submit Button state. The attributes on the buttons, when omitted, default to the values given on the corresponding the form element.

The action content attribute, if specified, must have a value that is a valid URL.

The action of an element is the value of the element's action attribute, if it has one, or the value of its form owner's action attribute, if it has one, or else the empty string.

The method content attribute is an enumerated attribute with the following keywords and states:

• The keyword GET, mapping to the state GET, indicating the HTTP GET method.
• The keyword POST, mapping to the state POST, indicating the HTTP POST method.
• The keyword PUT, mapping to the state PUT, indicating the HTTP PUT method.
• The keyword DELETE, mapping to the state DELETE, indicating the HTTP DELETE method.

The missing value default is the GET state.

The method of an element is one of those four states. If the element has a method attribute, then the element's method is that attribute's state; otherwise, it is the form owner's method attribute's state.

The enctype content attribute is an enumerated attribute with the following keywords and states:

• The "application/x-www-form-urlencoded" keyword and corresponding state.
• The "multipart/form-data" keyword and corresponding state.
• The "text/plain" keyword and corresponding state.

The missing value default is the application/x-www-form-urlencoded state.

The enctype of an element is one of those three states. If the element has a enctype attribute, then the element's enctype is that attribute's state; otherwise, it is the form owner's enctype attribute's state.

The target content attribute, if present, must be a valid browsing context name or keyword.

The target of an element is the value of the element's target attribute, if it has one; or the value of its form owner's target attribute, if it has one; or, if one of the child nodes of the head element is a base element with a target attribute, then the the value of the target attribute of the first such base element; or, if there is no such element, the empty string.

The novalidate content attribute is a boolean attribute. If present, it indicates that the form is not to be validated during submission.

The no-validate state of an element is true if the element's novalidate attribute is present or if the element's form owner's novalidate attribute is present, and false otherwise.

The action, method, enctype, and target DOM attributes must reflect the respective content attributes of the same name. The noValidate DOM attribute must reflect the novalidate content attribute.

4.10.14 Constraints

4.10.14.1 Definitions

A listed form-associated element is a candidate for constraint validation unless a condition has barred the element from constraint validation. (For example, an element is barred from constraint validation if it is an output or fieldset element.)

An element can have a custom validity error message defined. Initially, an element must have its custom validity error message set to the empty string. When its value is not the empty string, the element is suffering from a custom error. It can be set using the setCustomValidity() method. The user agent should use the custom validity error message when alerting the user to the problem with the control.

An element can be constrained in various ways. The following is the list of validity states that a form control can be in, making the control invalid for the purposes of constraint validation. (The definitions below are non-normative; other parts of this specification define more precisely when each state applies or does not.)

Suffering from being missing

When a control has no value but has a required attribute (input required, textarea required).

Suffering from a type mismatch

When a control that allows arbitrary user input has a value that is not in the correct syntax (E-mail, URL).

Suffering from a pattern mismatch

When a control has a value that doesn't satisfy the pattern attribute.

Suffering from being too long

When a control has a value that is too long for the form control maxlength attribute (input maxlength, textarea maxlength).

Suffering from an underflow

When a control has a value that is too low for the min attribute.

Suffering from an overflow

When a control has a value that is too high for the max attribute.

Suffering from a step mismatch

When a control has a value that doesn't fit the rules given by the step attribute.

Suffering from a custom error

When a control's custom validity error message (as set by the element's setCustomValidity() method) is not the empty string.

An element can still suffer from these states even when the element is disabled; thus these states can be represented in the DOM even if validating the form during submission wouldn't indicate a problem to the user.

An element satisfies its constraints if it is not suffering from any of the above validity states.

4.10.14.2 Constraint validation

When the user agent is required to statically validate the constraints of form element form, it must run the following steps, which return either a positive result (all the controls in the form are valid) or a negative result (there are invalid controls) along with a (possibly empty) list of elements that are invalid and for which no script has claimed responsibility:

1. Let controls be a list of all the submittable elements whose form owner is form, in tree order.

2. Let invalid controls be an initially empty list of elements.

3. For each element field in controls, in tree order, run the following substeps:

   1. If field is not a candidate for constraint validation, then move on to the next element.

   2. Otherwise, if field satisfies its constaints, then move on to the next element.

   3. Otherwise, add field to invalid controls.

4. If invalid controls is empty, then return a positive result and abort these steps.

5. Let unhandled invalid controls be an initially empty list of elements.

6. For each element field in invalid controls, if any, in tree order, run the following substeps:

   1. Fire a simple event named invalid at field.

   2. If the event was not canceled, then add field to unhandled invalid controls.

7. Return a negative result with the list of elements in the unhandled invalid controls list.

If a user agent is to interactively validate the constraints of form element form, then the user agent must run the following steps:

1. Statically validate the constraints of form, and let unhandled invalid controls be the list of elements returned if the result was negative.

2. If the result was positive, then return that result and abort these steps.

3. Report the problems with the constraints of at least one of the elements given in unhandled invalid controls to the user. User agents may focus one of those elements in the process, by running the focusing steps for that element, and may change the scrolling position of the document, or perform some other action that brings the element to the user's attention. User agents may report more than one constraint violation. User agents may coalesce related constraint violation reports if appropriate (e.g. if multiple radio buttons in a group are marked as required, only one error need be reported). If one of the controls is not visible to the user (e.g. it has the hidden attribute set) then user agents may report a script error.

4. Return a negative result.

4.10.14.3 The constraint validation API

The willValidate attribute must return true if an element is a candidate for constraint validation, and false otherwise (i.e. false if any conditions are barring it from constraint validation).

The setCustomValidity(message), when invoked, must set the custom validity error message to the value of the given message argument.

The validity attribute must return a ValidityState object that represents the validity states of the element. This object is live, and the same object must be returned each time the element's validity attribute is retrieved.

interface ValidityState {
  readonly attribute boolean valueMissing;
  readonly attribute boolean typeMismatch;
  readonly attribute boolean patternMismatch;
  readonly attribute boolean tooLong;
  readonly attribute boolean rangeUnderflow;
  readonly attribute boolean rangeOverflow;
  readonly attribute boolean stepMismatch;
  readonly attribute boolean customError;
  readonly attribute boolean valid;
};

A ValidityState object has the following attributes. On getting, they must return true if the corresponding condition given in the following list is true, and false otherwise.

valueMissing

The control is suffering from being missing.

typeMismatch

The control is suffering from a type mismatch.

patternMismatch

The control is suffering from a pattern mismatch.

tooLong

The control is suffering from being too long.

rangeUnderflow

The control is suffering from an underflow.

rangeOverflow

The control is suffering from an overflow.

stepMismatch

The control is suffering from a step mismatch.

customError

The control is suffering from a custom error.

valid

None of the other conditions are true.

When the checkValidity() method is invoked, if the element is a candidate for constraint validation and does not satisfy its constaints, the user agent must fire a simple event named invalid at the element and return false. Otherwise, it must only return true without doing anything else.

The validationMessage attribute must return the empty string if the element is not a candidate for constraint validation or if it is one but it satisfies its constaints; otherwise, it must return a suitably localised message that the user agent would show the user if this were the only form with a validity constraint problem. If the element is suffering from a custom error, then the custom validity error message should be present in the return value.

4.10.14.4 Security

Servers should not rely on client-side validation. Client-side validation can be intentionally bypassed by hostile users, and unintentionally bypassed by users of older user agents or automated tools that do not implement these features. The constraint validation features are only intended to improve the user experience, not to provide any kind of security mechanism.

4.10.15 Form submission

4.10.15.1 Implicit submission

User agents may establish a button in each form as being the form's default button. This should be the first submit button in tree order whose form owner is that form element, but user agents may pick another button if another would be more appropriate for the platform. If the platform supports letting the user submit a form implicitly (for example, on some platforms hitting the "enter" key while a text field is focused implicitly submits the form), then doing so must cause the form's default button's activation behavior, if any, to be run.

Consequently, if the default button is disabled, the form is not submitted when such an implicit submission mechanism is used. (A button has no activation behavior when disabled.)

If the form has no submit button, then the implicit submission mechanism must just submit the form element from the form element itself.

4.10.15.2 Form submission algorithm

When a form form is submitted from an element submitter (typically a button), the user agent must run the following steps:

1. If form is in a Document that has no associated browsing context or whose browsing context has its sandboxed forms browsing context flag set, then abort these steps without doing anything.

2. If form is already being submitted (i.e. the form was submitted again while processing the events fired from the next two steps, probably from a script redundantly calling the submit() method on form), then abort these steps. This doesn't affect the earlier instance of this algorithm.

3. If the submitter is anything but a form element, and the submitter element's no-validate state is false, then interactively validate the constraints of form and examine the result: if the result is negative (the constraint validation concluded that there were invalid fields and probably informed the user of this) then abort these steps.

4. If the submitter is anything but a form element, then fire a simple event that bubbles, named submit, at form. If the event's default action is prevented (i.e. if the event is canceled) then abort these steps. Otherwise, continue (effectively the default action is to perform the submission).

5. Let controls be a list of all the submittable elements whose form owner is form, in tree order.

6. Let the form data set be a list of name-value-type tuples, initially empty.

7. Constructing the form data set. For each element field in controls, in tree order, run the following substeps:

   1. If any of the following conditions are met, then skip these substeps for this element:

      • The field element has a datalist element ancestor.
      • The field element is disabled.
      • The field element is a button but it is not submitter.
      • The field element is an input element whose type attribute is in the Checkbox state and whose checkedness is false.
      • The field element is an input element whose type attribute is in the Radio Button state and whose checkedness is false.
      • The field element is an input element whose type attribute is in the File Upload state but the control does not have any files selected.
      • The field element is an object element that is not using a plugin.

      Otherwise, process field as follows:

   2. Let type be the value of the type DOM attribute of field.

   3. If the field element is an input element whose type attribute is in the Image Button state, then run these further nested substeps:

      1. If the field element has an name attribute specified and value is not the empty string, let name be that value followed by a single U+002E FULL STOP (.) character. Otherwise, let name be the empty string.

      2. Let name_x be the string consisting of the concatenation of name and a single U+0078 LATIN SMALL LETTER X (x) character.

      3. Let name_y be the string consisting of the concatenation of name and a single U+0079 LATIN SMALL LETTER Y (y) character.

      4. The field element is submitter, and before this algorithm was invoked the user indicated a coordinate. Let x be the x-component of the coordindate selected by the user, and let y be the y-component of the coordinate selected by the user.

      5. Append an entry in the form data set with the name name_x, the value x, and the type type.

      6. Append an entry in the form data set with the name name_y and the value y, and the type type.

      7. Skip the remaining substeps for this element: if there are any more elements in controls, return to the top of the constructing the form data set step, otherwise, jump to the next step in the overall form submission algorithm.

   4. If the field element does not have a name attribute specified, or its name attribute's value is the empty string, skip these substeps for this element: if there are any more elements in controls, return to the top of the constructing the form data set step, otherwise, jump to the next step in the overall form submission algorithm.

   5. Let name be the value of the field element's name attribute.

   6. If the field element is a select element, then for each option element in the select element whose selectedness is true, append an entry in the form data set with the name as the name, the value of the option element as the value, and type as the type.

   7. Otherwise, if the field element is an input element whose type attribute is in the Checkbox state or the Radio Button state, then then run these further nested substeps:

      1. If the field element has a value attribute specified, then let value be the value of that attribute; otherwise, let value be the string "on".

      2. Append an entry in the form data set with name as the name, value as the value, and type as the type.

   8. Otherwise, if the field element is an input element whose type attribute is in the File Upload state, then for each file selected in the input element, append an entry in the form data set with the name as the name, the file (consisting of the name, the type, and the body) as the value, and type as the type.

   9. Otherwise, if the field element is an object element: try to obtain a form submission value from the plugin, and if that is successful, append an entry in the form data set with name as the name, the returned form submission value as the value, and the string "object" as the type.

   10. Otherwise, append an entry in the form data set with name as the name, the value of the field element as the value, and type as the type.

8. Let action be the submitter element's action.

9. If action is the empty string, let action be the document's address.

   This step is a willful violation of RFC 3986. [RFC3986]

10. Resolve the URL action, relative to the submitter element. If this fails, abort these steps. Otherwise, let action be the resulting absolute URL.

11. Let scheme be the <scheme> of the resulting absolute URL.

12. Let enctype be the submitter element's enctype.

13. Let method be the submitter element's method.

14. Let target be the submitter element's target.

15. Select the appropriate row in the table below based on the value of scheme as given by the first cell of each row. Then, select the appropriate cell on that row based on the value of method as given in the first cell of each column. Then, jump to the steps named in that cell and defined below the table.

    	GET	POST	PUT	DELETE
    http	Mutate action	Submit as entity body	Submit as entity body	Delete action
    https	Mutate action	Submit as entity body	Submit as entity body	Delete action
    ftp	Get action	Get action	Get action	Get action
    javascript	Get action	Get action	Get action	Get action
    data	Get action	Post to data:	Put to data:	Get action
    mailto	Mail with headers	Mail as body	Mail with headers	Mail with headers

    If scheme is not one of those listed in this table, then the behavior is not defined by this specification. User agents should, in the absence of another specification defining this, act in a manner analogous to that defined in this specification for similar schemes.

    The behaviors are as follows:

    Mutate action

    Let query be the result of encoding the form data set using the application/x-www-form-urlencoded encoding algorithm, interpreted as a US-ASCII string.

    Let destination be a new URL that is equal to the action except that its <query> component is replaced by query (adding a U+003F QUESTION MARK (?) character if appropriate).

    Let target browsing context be the form submission target browsing context.

    Navigate target browsing context to destination. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

    Submit as entity body

    Let entity body be the result of encoding the form data set using the appropriate form encoding algorithm.

    Let target browsing context be the form submission target browsing context.

    Let MIME type be determined as follows:

    If enctype is application/x-www-form-urlencoded

    Let MIME type be "application/x-www-form-urlencoded".

    If enctype is multipart/form-data

    Let MIME type be "multipart/form-data".

    If enctype is text/plain

    Let MIME type be "text/plain".

    Navigate target browsing context to action using the HTTP method given by method and with entity body as the entity body, of type MIME type. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

    Delete action

    Let target browsing context be the form submission target browsing context.

    Navigate target browsing context to action using the DELETE method. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

    Get action

    Let target browsing context be the form submission target browsing context.

    Navigate target browsing context to action. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

    Post to data:

    Let data be the result of encoding the form data set using the appropriate form encoding algorithm.

    If action contains the string "%%%%" (four U+0025 PERCENT SIGN characters), then %-escape all bytes in data that, if interpreted as US-ASCII, do not match the unreserved production in the URI Generic Syntax, and then, treating the result as a US-ASCII string, further %-escape all the U+0025 PERCENT SIGN characters in the resulting string and replace the first occurance of "%%%%" in action with the resulting double-escaped string. [RFC3986]

    Otherwise, if action contains the string "%%" (two U+0025 PERCENT SIGN characters in a row, but not four), then %-escape all characters in data that, if interpreted as US-ASCII, do not match the unreserved production in the URI Generic Syntax, and then, treating the result as a US-ASCII string, replace the first occurance of "%%" in action with the resulting escaped string. [RFC3986]

    Let target browsing context be the form submission target browsing context.

    Navigate target browsing context to the potentially modified action. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

    Put to data:

    Let data be the result of encoding the form data set using the appropriate form encoding algorithm.

    Let MIME type be determined as follows:

    If enctype is application/x-www-form-urlencoded

    Let MIME type be "application/x-www-form-urlencoded".

    If enctype is multipart/form-data

    Let MIME type be "multipart/form-data".

    If enctype is text/plain

    Let MIME type be "text/plain".

    Let destination be the result of concatenating the following:

    1. The string "data:".
    2. The value of MIME type.
    3. The string ";base64,".
    4. A base-64 encoded representation of data. [RFC2045]

    Let target browsing context be the form submission target browsing context.

    Navigate target browsing context to destination. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

    Mail with headers

    Let headers be the resulting encoding the form data set using the application/x-www-form-urlencoded encoding algorithm, interpreted as a US-ASCII string.

    Replace occurances of U+002B PLUS SIGN characters (+) in headers with the string "%20".

    Let destination consist of all the characters from the first character in action to the character immediately before the first U+003F QUESTION MARK character (?), if any, or the end of the string if there are none.

    Append a single U+003F QUESTION MARK character (?) to destination.

    Append headers to destination.

    Let target browsing context be the form submission target browsing context.

    Navigate target browsing context to destination. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

    Mail as body

    Let body be the resulting encoding the form data set using the appropriate form encoding algorithm and then %-escaping all the bytes in the resulting byte string that, when interpreted as US-ASCII, do not match the unreserved production in the URI Generic Syntax. [RFC3986]

    Let destination have the same value as action.

    If destination does not contain a U+003F QUESTION MARK character (?), append a single U+003F QUESTION MARK character (?) to destination. Otherwise, append a single U+0026 AMPERSAND character (&).

    Append the string "body=" to destination.

    Append body, interpreted as a US-ASCII string, to destination.

    Let target browsing context be the form submission target browsing context.

    Navigate target browsing context to destination. If target browsing context was newly created for this purpose by the steps above, then it must be navigated with replacement enabled.

    The form submission target browsing context is obtained, when needed by the behaviors described above, as follows: If the user indicated a specific browsing context to use when submitting the form, then that is the target browsing context. Otherwise, apply the rules for choosing a browsing context given a browsing context name using target as the name and the browsing context of form as the context in which the algorithm is executed; the resulting browsing context is the target browsing context.

    The appropriate form encoding algorithm is determined as follows:

    If enctype is application/x-www-form-urlencoded

    Use the application/x-www-form-urlencoded encoding algorithm.

    If enctype is multipart/form-data

    Use the multipart/form-data encoding algorithm.

    If enctype is text/plain

    Use the text/plain encoding algorithm.