Some IDL attributes are defined to reflect a particular content attribute. This means that on getting, the IDL attribute returns the current value of the content attribute, and on setting, the IDL attribute changes the value of the content attribute to the given value.
The HTMLAllCollection
,
HTMLFormControlsCollection
,
HTMLOptionsCollection
,
interfaces are collections derived from the
HTMLCollection
interface.
The HTMLAllCollection
interface represents a generic
collection of elements just like
HTMLCollection
, with the exception that its namedItem()
method
returns an HTMLAllCollection
object when there are
multiple matching elements, and that its item()
method can be used
as a synonym for its namedItem()
method.
interface HTMLAllCollection : HTMLCollection { // inherits length and item(unsigned long index) object? item(DOMString name); legacycaller getter object? namedItem(DOMString name); // overrides inherited namedItem() HTMLAllCollection tags(DOMString tagName); };
length
Returns the number of elements in the collection.
item
(index)Returns the item with index index from the collection. The items are sorted in tree order.
item
(name)item
(name)namedItem
(name)namedItem
(name)Returns the item with ID or name name from the collection.
If there are multiple matching items, then an HTMLAllCollection
object containing all those elements is returned.
Only a
, applet
, area
,
embed
, form
, frame
,
frameset
, iframe
, img
, and
object
elements can have a name for the purpose of
this method; their name is given by the value of their name
attribute.
tags
(tagName)Returns a collection that is a filtered view of the current collection, containing only elements with the given tag name.
The HTMLFormControlsCollection
interface represents
a collection of listed elements in form
and fieldset
elements.
interface HTMLFormControlsCollection : HTMLCollection { // inherits length and item() legacycaller getter object? namedItem(DOMString name); // overrides inherited namedItem() }; interface RadioNodeList : NodeList { attribute DOMString value; };
length
Returns the number of elements in the collection.
item
(index)Returns the item with index index from the collection. The items are sorted in tree order.
namedItem
(name)namedItem
(name)Returns the item with ID or name
name from the collection.
If there are multiple matching items, then a RadioNodeList
object containing all those elements is returned.
Returns the value of the first checked radio button represented by the object.
Can be set, to check the first radio button with the given value represented by the object.
The HTMLOptionsCollection
interface represents a
list of option
elements. It is always rooted on a
select
element and has attributes and methods that
manipulate that element's descendants.
interface HTMLOptionsCollection : HTMLCollection {
// inherits item()
attribute unsigned long length; // overrides inherited length
legacycaller getter object? namedItem(DOMString name); // overrides inherited namedItem()
setter creator void (unsigned long index, HTMLOptionElement option);
void add((HTMLOptionElement or HTMLOptGroupElement) element, optional (HTMLElement or long)? before = null);
void remove(long index);
attribute long selectedIndex;
};
length
[ = value ]Returns the number of elements in the collection.
When set to a smaller number, truncates the number of option
elements in the corresponding container.
When set to a greater number, adds new blank option
elements to that container.
item
(index)Returns the item with index index from the collection. The items are sorted in tree order.
namedItem
(name)namedItem
(name)Returns the item with ID or name
name from the collection.
If there are multiple matching items, then a NodeList
object containing all those elements is returned.
add
(element [, before ] )Inserts element before the node given by before.
The before argument can be a number, in which case element is inserted before the item with that number, or an element from the collection, in which case element is inserted before that element.
If before is omitted, null, or a number out of range, then element will be added at the end of the list.
This method will throw a HierarchyRequestError
exception if element is an ancestor of the
element into which it is to be inserted.
selectedIndex
[ = value ]Returns the index of the first selected item, if any, or −1 if there is no selected item.
Can be set, to change the selection.
The DOMStringMap
interface represents a set of
name-value pairs. It exposes these using the scripting language's
native mechanisms for property access.
The dataset
attribute on
elements exposes the data-*
attributes on the element.
Given the following fragment and elements with similar constructions:
<img class="tower" id="tower5" data-x="12" data-y="5" data-ai="robotarget" data-hp="46" data-ability="flames" src="towers/rocket.png alt="Rocket Tower">
...one could imagine a function splashDamage()
that takes some arguments, the first
of which is the element to process:
function splashDamage(node, x, y, damage) { if (node.classList.contains('tower') && // checking the 'class' attribute node.dataset.x == x && // reading the 'data-x' attribute node.dataset.y == y) { // reading the 'data-y' attribute var hp = parseInt(node.dataset.hp); // reading the 'data-hp' attribute hp = hp - damage; if (hp < 0) { hp = 0; node.dataset.ai = 'dead'; // setting the 'data-ai' attribute delete node.dataset.ability; // removing the 'data-ability' attribute } node.dataset.hp = hp; // setting the 'data-hp' attribute } }
Some objects support being copied and closed in one operation. This is called transferring the object, and is used in particular to transfer ownership of unsharable or expensive resources across worker boundaries.
[NoInterfaceObject] interface Transferable { };
The following Transferable
types exist:
MessagePort
DOM3 Core defines mechanisms for checking for interface support, and for obtaining implementations of interfaces, using feature strings. [DOMCORE]
Authors are strongly discouraged from using these, as they are notoriously unreliable and imprecise. Authors are encouraged to rely on explicit feature testing or the graceful degradation behavior intrinsic to some of the features in this specification.