input
element attributes
autocomplete
attributedirname
attributelist
attributereadonly
attributesize
attributerequired
attributemultiple
attributemaxlength
attributepattern
attributemin
and max
attributesstep
attributeplaceholder
attributeinput
element APIsinput
element attributesautocomplete
attributeUser agents sometimes have features for helping users fill forms in, for example prefilling the user's address based on earlier user input.
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 either that the control's input data is particularly sensitive (for example the activation code for a nuclear weapon); or that it 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; or that the document provides its own autocomplete mechanism and does not want the user agent to provide autocompletion values.
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. (By default, the autocomplete
attribute of
form
elements is in the on state.)
Banks frequently do not want UAs to prefill login information:
<p><label>Account: <input type="text" name="ac" autocomplete="off"></label></p> <p><label>PIN: <input type="password" name="pin" autocomplete="off"></label></p>
dirname
attributeThe dirname
attribute, when it applies, is a form control dirname
attribute.
In this example, a form contains a text field and a submission button:
<form action="addcomment.cgi" method=post> <p><label>Comment: <input type=text name="comment" dirname="comment.dir" required></label></p> <p><button name="mode" type=submit value="add">Post Comment</button></p> </form>
When the user submits the form, the user agent includes three fields, one called "comment", one called "comment.dir", and one called "mode"; so if the user types "Hello", the submission body might be something like:
comment=Hello&comment.dir=ltr&mode=add
If the user manually switches to a right-to-left writing direction and enters "مرحبًا", the submission body might be something like:
comment=%D9%85%D8%B1%D8%AD%D8%A8%D9%8B%D8%A7&comment.dir=rtl&mode=add
list
attributeThe 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.
This URL field offers some suggestions.
<label>Homepage: <input name=hp type=url list=hpurls></label> <datalist id=hpurls> <option value="http://www.google.com/" label="Google"> <option value="http://www.reddit.com/" label="Reddit"> </datalist>
Other URLs from the user's history might show also; this is up to the user agent.
This example demonstrates how to design a form that uses the autocompletion list feature while still degrading usefully in legacy user agents.
If the autocompletion list is merely an aid, and is not
important to the content, then simply using a datalist
element with children option
elements is enough. To
prevent the values from being rendered in legacy user agents, they
should be placed inside the value
attribute instead of
inline.
<p> <label> Enter a breed: <input type="text" name="breed" list="breeds"> <datalist id="breeds"> <option value="Abyssinian"> <option value="Alpaca"> <!-- ... --> </datalist> </label> </p>
However, if the values need to be shown in legacy UAs, then
fallback content can be placed inside the datalist
element, as follows:
<p> <label> Enter a breed: <input type="text" name="breed" list="breeds"> </label> <datalist id="breeds"> <label> or select one from the list: <select name="breed"> <option value=""> (none selected) <option>Abyssinian <option>Alpaca <!-- ... --> </select> </label> </datalist> </p>
The fallback content will only be shown in UAs that don't
support datalist
. The options, on the other hand, will
be detected by all UAs, even though they are not direct children of
the datalist
element.
Note that if an option
element used in a
datalist
is selected
, it will be selected
by default by legacy UAs (because it affects the
select
), but it will not have any effect on the
input
element in UAs that support
datalist
.
readonly
attributeThe readonly
attribute is a boolean attribute that controls whether
or not the user can edit the form control.
In the following example, the existing product identifiers cannot be modified, but they are still displayed as part of the form, for consistency with the row representing a new product (where the identifier is not yet filled in).
<form action="products.cgi" method=post enctype="multipart/form-data"> <table> <tr> <th> Product ID <th> Product name <th> Price <th> Action <tr> <td> <input readonly name="1.pid" value="H412"> <td> <input required name="1.pname" value="Floor lamp Ulke"> <td> $<input required type=number min=0 step=0.01 name="1.pprice" value="49.99"> <td> <button formnovalidate name="action" value="delete:1">Delete</button> <tr> <td> <input readonly name="2.pid" value="FG28"> <td> <input required name="2.pname" value="Table lamp Ulke"> <td> $<input required type=number min=0 step=0.01 name="2.pprice" value="24.99"> <td> <button formnovalidate name="action" value="delete:2">Delete</button> <tr> <td> <input required name="3.pid" value="" pattern="[A-Z0-9]+"> <td> <input required name="3.pname" value=""> <td> $<input required type=number min=0 step=0.01 name="3.pprice" value=""> <td> <button formnovalidate name="action" value="delete:3">Delete</button> </table> <p> <button formnovalidate name="action" value="add">Add</button> </p> <p> <button name="action" value="update">Save</button> </p> </form>
size
attributeThe 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.
required
attributeThe required
attribute is a boolean attribute. When specified, the
element is required.
The following form has two required fields, one for an e-mail address and one for a password. It also has a third field that is only considerd valid if the user types the same password in the password field and this third field.
<h1>Create new account</h1> <form action="/newaccount" method=post oninput="up2.setCustomValidity(up2.value != up.value ? 'Passwords do not match.' : '')"> <p> <label for="username">E-mail address:</label> <input id="username" type=email required name=un> <p> <label for="password1">Password:</label> <input id="password1" type=password required name=up> <p> <label for="password2">Confirm password:</label> <input id="password2" type=password name=up2> <p> <input type=submit value="Create account"> </form>
multiple
attributeThe multiple
attribute is a boolean attribute that indicates whether
the user is to be allowed to specify more than one value.
The following extract shows how an e-mail client's "Cc" field could accept multiple e-mail addresses.
<label>Cc: <input type=email multiple name=cc></label>
If the user had, amongst many friends in his user contacts database, two friends "Arthur Dent" (with address "art@example.net") and "Adam Josh" (with address "adamjosh@example.net"), then, after the user has typed "a", the user agent might suggest these two e-mail addresses to the user.
The page could also link in the user's contacts database from the site:
<label>Cc: <input type=email multiple name=cc list=contacts></label> ... <datalist id="contacts"> <option value="hedral@damowmow.com"> <option value="pillar@example.com"> <option value="astrophy@cute.example"> <option value="astronomy@science.example.org"> </datalist>
Suppose the user had entered "bob@example.net" into this text
field, and then started typing a second e-mail address starting
with "a". The user agent might show both the two friends mentioned
earlier, as well as the "astrophy" and "astronomy" values given in
the datalist
element.
The following extract shows how an e-mail client's "Attachments" field could accept multiple files for upload.
<label>Attachments: <input type=file multiple name=att></label>
maxlength
attributeThe maxlength
attribute is a form control maxlength
attribute.
If the input
element has a maximum allowed
value length, then the code-point length of the
value of the element's value
attribute must be equal to or less than the element's maximum
allowed value length.
The following extract shows how a messaging client's text entry could be arbitrarily restricted to a fixed number of characters, thus forcing any conversation through this medium to be terse and discouraging intelligent discourse.
What are you doing? <input name=status maxlength=140>
pattern
attributeThe pattern
attribute specifies a regular expression against which the control's
value, or, when the multiple
attribute applies and is
set, the control's values, are to be
checked.
If specified, the attribute's value must match the JavaScript Pattern production. [ECMA262]
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.
For example, the following snippet:
<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>
...could cause the UA to display an alert such as:
A part number is a digit followed by three uppercase letters. You cannot submit this form when the field is incorrect.
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 title
s as if an
error has necessarily occurred.
min
and max
attributesThe min
and max
attributes indicate
the allowed range of values for the element.
The max
attribute's value
(the maximum) must not be
less than the min
attribute's
value (its minimum).
The following date control limits input to dates that are before the 1980s:
<input name=bday type=date max="1979-12-31">
The following number control limits input to whole numbers greater than zero:
<input name=quantity required type=number min=1 value=1>
step
attributeThe step
attribute indicates the granularity that is expected (and required)
of the value, by limiting the
allowed values.
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 following range control only accepts values in the range 0..1, and allows 256 steps in that range:
<input name=opacity type=range min=0 max=1 step=0.00392156863>
The following control allows any time in the day to be selected, with any accuracy (e.g. thousandth-of-a-second accuracy or more):
<input name=favtime type=time step=any>
Normally, time controls are limited to an accuracy of one minute.
placeholder
attributeThe 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
.
Here is an example of a mail configuration user interface that
uses the placeholder
attribute:
<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>
input
element APIsvalue
[ = value ]Returns the current value of the form control.
Can be set, to change the value.
Throws an INVALID_STATE_ERR
exception if it is
set to any value other than the empty string when the control is a
file upload control.
checked
[ = value ]Returns the current checkedness of the form control.
Can be set, to change the checkedness.
files
Returns a FileList
object listing the selected files of
the form control.
Returns null if the control isn't a file control.
valueAsDate
[ = value ]Returns a Date
object representing the form
control's value, if
applicable; otherwise, returns null.
Can be set, to change the value.
Throws an INVALID_STATE_ERR
exception if the
control isn't date- or time-based.
valueAsNumber
[ = value ]Returns a number representing the form control's value, if applicable; otherwise, returns null.
Can be set, to change the value.
Throws an INVALID_STATE_ERR
exception if the
control is neither date- or time-based nor numeric.
stepUp
( [ n ] )stepDown
( [ n ] )Changes the form control's value by the value given in the
step
attribute, multiplied by
n. The default value for n
is 1.
Throws INVALID_STATE_ERR
exception if the control
is neither date- or time-based nor numeric, if the step
attribute's value is "any
", if the current value could not be parsed, or if
stepping in the given direction by the given amount would take the
value out of range.
list
Returns the datalist
element indicated by the
list
attribute.
selectedOption
Returns the option
element from the
datalist
element indicated by the list
attribute that matches the
form control's value.