2.5 URLs

2.5.1 Terminology

A URL is a valid URL if it conforms to the authoring conformance requirements in the URL standard. [URL]

A string is a valid non-empty URL if it is a valid URL but it is not the empty string.

A string is a valid URL potentially surrounded by spaces if, after stripping leading and trailing whitespace from it, it is a valid URL.

A string is a valid non-empty URL potentially surrounded by spaces if, after stripping leading and trailing whitespace from it, it is a valid non-empty URL.

This specification defines the URL about:legacy-compat as a reserved, though unresolvable, about: URL, for use in DOCTYPEs in HTML documents when needed for compatibility with XML tools. [ABOUT]

This specification defines the URL about:srcdoc as a reserved, though unresolvable, about: URL, that is used as the document's address of iframe srcdoc documents. [ABOUT]

The fallback base URL of a Document object is the absolute URL obtained by running these substeps:

  1. If the Document is an iframe srcdoc document, then return the document base URL of the Document's browsing context's browsing context container's Document and abort these steps.

  2. If the document's address is about:blank, and the Document's browsing context has a creator browsing context, then return the document base URL of the creator Document, and abort these steps.

  3. Return the document's address.

The document base URL of a Document object is the absolute URL obtained by running these substeps:

  1. If there is no base element that has an href attribute in the Document, then the document base URL is the Document's fallback base URL; abort these steps.

  2. Otherwise, the document base URL is the frozen base URL of the first base element in the Document that has an href attribute, in tree order.

2.5.2 CORS settings attributes

A CORS settings attribute 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.

Keyword State Brief description
anonymous Anonymous Cross-origin CORS requests for the element will have the omit credentials flag set.
use-credentials Use Credentials Cross-origin CORS requests for the element will not have the omit credentials flag set.

The empty string is also a valid keyword, and maps to the Anonymous state. The attribute's invalid value default is the Anonymous state. For the purposes of reflection, the canonical case for the Anonymous state is the anonymous keyword. The missing value default, used when the attribute is omitted, is the No CORS state.

2.6 Common DOM interfaces

2.6.1 Reflecting content attributes in IDL attributes

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.

2.6.2 Collections

The HTMLAllCollection, HTMLFormControlsCollection, HTMLOptionsCollection, and HTMLPropertiesCollection interfaces are collections derived from the HTMLCollection interface.

2.6.2.1 HTMLAllCollection

The HTMLAllCollection interface is used for generic collections of elements just like HTMLCollection, with the exception that its namedItem() method returns an HTMLCollection object when there are multiple matching elements, and that its item() method can be used as a synonym for its namedItem() method. It is intended only for the legacy document.all attribute.

interface HTMLAllCollection : HTMLCollection {
  // inherits length and item(unsigned long index)
  (HTMLCollection or Element)? item(DOMString name);
  legacycaller getter (HTMLCollection or Element)? namedItem(DOMString name); // shadows inherited namedItem()
  HTMLAllCollection tags(DOMString tagName);
};
collection . length

Returns the number of elements in the collection.

element = collection . item(index)
collection[index]

Returns the item with index index from the collection. The items are sorted in tree order.

element = collection . item(name)
collection = collection . item(name)
element = collection . namedItem(name)
collection = collection . namedItem(name)
collection[name]
collection(name)

Returns the item with ID or name name from the collection.

If there are multiple matching items, then an HTMLCollection 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.

collection = collection . tags(tagName)

Returns a collection that is a filtered view of the current collection, containing only elements with the given tag name.

2.6.2.2 HTMLFormControlsCollection

The HTMLFormControlsCollection interface is used for collections of listed elements in form and fieldset elements.

interface HTMLFormControlsCollection : HTMLCollection {
  // inherits length and item()
  legacycaller getter (RadioNodeList or Element)? namedItem(DOMString name); // shadows inherited namedItem()
};

interface RadioNodeList : NodeList {
          attribute DOMString value;
};
collection . length

Returns the number of elements in the collection.

element = collection . item(index)
collection[index]

Returns the item with index index from the collection. The items are sorted in tree order.

element = collection . namedItem(name)
radioNodeList = collection . namedItem(name)
collection[name]
collection(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.

radioNodeList . value [ = value ]

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.

2.6.2.3 HTMLOptionsCollection

The HTMLOptionsCollection interface is used for collections 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; // shadows inherited length
  legacycaller HTMLOptionElement? (DOMString name);
  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;
};
collection . 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.

element = collection . item(index)
collection[index]

Returns the item with index index from the collection. The items are sorted in tree order.

element = collection . namedItem(name)
nodeList = collection . namedItem(name)
collection[name]
collection(name)

Returns the item with ID or name name from the collection.

If there are multiple matching items, then the first is returned.

collection . 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.

collection . 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.

2.6.2.4 HTMLPropertiesCollection

The HTMLPropertiesCollection interface is used for collections of elements that add name-value pairs to a particular item in the microdata model.

interface HTMLPropertiesCollection : HTMLCollection {
  // inherits length and item()
  getter PropertyNodeList? namedItem(DOMString name); // shadows inherited namedItem()
  readonly attribute DOMString[] names;
};

typedef sequence<any> PropertyValueArray;

interface PropertyNodeList : NodeList {
  PropertyValueArray getValues();
};
collection . length

Returns the number of elements in the collection.

element = collection . item(index)
collection[index]

Returns the element with index index from the collection. The items are sorted in tree order.

propertyNodeList = collection . namedItem(name)

Returns a PropertyNodeList object containing any elements that add a property named name.

collection[name]

Returns a PropertyNodeList object containing any elements that add a property named name. The name index has to be one of the values listed in the names list.

collection . names

Returns an array with the property names of the elements in the collection.

propertyNodeList . getValues()

Returns an array of the various values that the relevant elements have.

2.6.3 DOMStringMap

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
  }
}

2.6.4 DOMElementMap

The DOMElementMap interface represents a set of name-element mappings. It exposes these using the scripting language's native mechanisms for property access.

2.6.5 Transferable objects

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.

The following Transferable types exist:

2.6.6 Callbacks

The following callback function type is used in various APIs that interact with File objects:

callback FileCallback = void (File file);

2.7 Namespaces

The HTML namespace is: http://www.w3.org/1999/xhtml

The MathML namespace is: http://www.w3.org/1998/Math/MathML

The SVG namespace is: http://www.w3.org/2000/svg

The XLink namespace is: http://www.w3.org/1999/xlink

The XML namespace is: http://www.w3.org/XML/1998/namespace

The XMLNS namespace is: http://www.w3.org/2000/xmlns/


Data mining tools and other user agents that perform operations on content without running scripts, evaluating CSS or XPath expressions, or otherwise exposing the resulting DOM to arbitrary content, may "support namespaces" by just asserting that their DOM node analogues are in certain namespaces, without actually exposing the above strings.


In the HTML syntax, namespace prefixes and namespace declarations do not have the same effect as in XML. For instance, the colon has no special meaning in HTML element names.