W3C DOM 4.1

1. Conformance

All diagrams, examples, and notes in this specification are non-normative, as are all sections explicitly marked non-normative. Everything else in this specification is normative.

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119. For readability, these words do not appear in all uppercase letters in this specification. [RFC2119]

Requirements phrased in the imperative as part of algorithms (such as "strip any leading space characters" or "return false and terminate these steps") are to be interpreted with the meaning of the keywords ("must", "should", "may", etc.) used in introducing the algorithm.

Conformance requirements phrased as algorithms or specific steps may be implemented in any manner, so long as the end result is equivalent. (In particular, the algorithms defined in this specification are intended to be easy to follow, and not intended to be performant.)

User agents may impose implementation-specific limits on otherwise unconstrained inputs, e.g. to prevent denial of service attacks, to guard against running out of memory, or to work around platform-specific limitations.

When a method or an attribute is said to call another method or attribute, the user agent must invoke its internal API for that attribute or method so that e.g. the author can’t change the behavior by overriding attributes or methods with custom properties or functions in JavaScript.

Unless otherwise stated, string comparisons are done in a case-sensitive manner.

1.1. Dependencies

The IDL fragments in this specification must be interpreted as required for conforming IDL fragments, as described in the Web IDL specification. [WEBIDL]

Some of the terms used in this specification are defined in Encoding, Selectors, WEBIDL, XML, and Namespaces in XML.[ENCODING][SELECTORS4][WEBIDL][XML][XML-NAMES]

1.2. Extensibility

Vendor-specific proprietary extensions to this specification are strongly discouraged. Authors must not use such extensions, as doing so reduces interoperability and fragments the user base, allowing only users of specific user agents to access the content in question.

When extensions are needed, the DOM Standard can be updated accordingly, or a new standard can be written that hooks into the provided extensibility hooks for applicable specifications.

2. Terminology

The term context object means the object on which the algorithm, attribute getter, attribute setter, or method being discussed was called. When the context object is unambiguous, the term can be omitted.

2.1. Trees

A tree is a finite hierarchical tree structure. In tree order is preorder, depth-first traversal of a tree.

An object that participates in a tree has a parent, which is either another object or null, and an ordered list of zero or more child objects. An object A whose parent is object B is a child of B.

The root of an object is itself, if its parent is null, or else it is the root of its parent.

An object A is called a descendant of an object B, if either A is a child of B or A is a child of an object C that is a descendant of B.

An inclusive descendant is an object or one of its descendants.

An object A is called an ancestor of an object B if and only if B is a descendant of A.

An inclusive ancestor is an object or one of its ancestors.

An object A is called a sibling of an object B, if and only if B and A share the same non-null parent.

An object A is preceding an object B if A and B are in the same tree and A comes before B in tree order.

An object A is following an object B if A and B are in the same tree and A comes after B in tree order.

The first child of an object is its first child or null if it has no children.

The last child of an object is its last child or null if it has no children.

The previous sibling of an object is its first preceding sibling or null if it has no preceding sibling.

The next sibling of an object is its first following sibling or null if it has no following sibling.

The index of an object is its number of preceding siblings.

2.2. Strings

Comparing two strings in a case-sensitive manner means comparing them exactly, code point for code point.

Comparing two strings in a ASCII case-insensitive manner means comparing them exactly, code point for code point, except that the characters in the range U+0041 to U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z), inclusive, and the corresponding characters in the range U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z), inclusive, are considered to also match.

Converting a string to ASCII uppercase means replacing all characters in the range U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z), inclusive, with the corresponding characters in the range U+0041 to U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z).

Converting a string to ASCII lowercase means replacing all characters in the range U+0041 to U+005A (i.e. LATIN CAPITAL LETTER A to LATIN CAPITAL LETTER Z), inclusive, with the corresponding characters in the range U+0061 to U+007A (i.e. LATIN SMALL LETTER A to LATIN SMALL LETTER Z).

A string pattern is a prefix match for a string s when pattern is not longer than s and truncating s to pattern’s length leaves the two strings as matches of each other.

2.3. Ordered sets

An ordered set is a list that it must not contain the same item twice.

The ordered set parser takes a string input and then runs these steps:

1. Let position be a pointer into input, initially pointing at the start of the string.
2. Let tokens be an ordered set of tokens, initially empty.
3. Skip ASCII whitespace.

4. While position is not past the end of input:

   1. Collect a code point sequence of code points that are not ASCII whitespace.
   2. If the collected string is not in tokens, append the collected string to tokens.
   3. Skip ASCII whitespace.
5. Return tokens.

To replace within an ordered set set, given item and replacement, if item or replacement is in set, then replace the first instance of either with replacement and remove all other instances.

To collect a code point sequence of code points, run these steps:

1. Let input and position be the same variables as those of the same name in the algorithm that invoked these steps.
2. Let result be the empty string.
3. While position does not point past the end of input and the code point at position is one of code points, append that code point to the end of result and advance position to the next code point in input.
4. Return result.

To skip ASCII whitespace means to collect a code point sequence of ASCII whitespace and discard the return value.

The ordered set serializer takes a set and returns the concatenation of the strings in set, separated from each other by U+0020, if set is non-empty.

2.4. Selectors

To scope-match a selectors string selectors against a node, run these steps:

1. Let s be the result of parse a selector selectors. [SELECTORS4]

2. If s is failure, then throw a SyntaxError.

3. Return the result of evaluate a selector s against node’s root using scoping root node. [SELECTORS4].

Support for namespaces within selectors is not planned and will not be added.

2.5. Namespaces

To validate a qualifiedName, run these steps:

1. If qualifiedName does not match the Name production, then throw an InvalidCharacterError.

2. If qualifiedName does not match the QName production, then throw a NamespaceError.

To validate and extract a namespace and qualifiedName, run these steps:

1. If namespace is the empty string, set it to null.
2. Validate qualifiedName. Rethrow any exceptions.
3. Let prefix be null.
4. Let localName be qualifiedName.
5. If qualifiedName contains a ":" (U+003E), then split the string on it and set prefix to the part before and localName to the part after.
6. If prefix is non-null and namespace is null, then throw a NamespaceError.
7. If prefix is "xml" and namespace is not the XML namespace, then throw a NamespaceError.
8. If either qualifiedName or prefix is "xmlns" and namespace is not the XMLNS namespace, then throw a NamespaceError.
9. If namespace is the XMLNS namespace and neither qualifiedName nor prefix is "xmlns", then throw a NamespaceError.
10. Return namespace, prefix, and localName.

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

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

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

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

3. Events

3.1. Introduction to "DOM Events"

Throughout the web platform events are dispatched to objects to signal an occurrence, such as network activity or user interaction. These objects implement the EventTarget interface and can therefore add event listeners to observe events by calling addEventListener():

obj.addEventListener("load", imgFetched)
function imgFetched(ev) {
  // great success
  …
}

Event listeners can be removed by utilizing the removeEventListener() method, passing the same arguments.

Events are objects too and implement the Event interface (or a derived interface). In the example above ev is the event. It is passed as argument to event listener’s callback (typically a JavaScript Function as shown above).

Event listeners key off the event’s type attribute value ("load" in the above example). The event’s target attribute value returns the object to which the event was dispatched (obj above).

Now while typically events are dispatched by the user agent as the result of user interaction or the completion of some task, applications can dispatch events themselves, commonly known as synthetic events:

// add an appropriate event listener
obj.addEventListener("cat", function(e) { process(e.detail) })

// create and dispatch the event
var event = new CustomEvent("cat", {"detail":{"hazcheeseburger":true}})
obj.dispatchEvent(event)

Apart from signaling, events are sometimes also used to let an application control what happens next in an operation. For instance as part of form submission an event whose type attribute value is "submit" is dispatched. If this event’s preventDefault() method is invoked, form submission will be terminated. Applications who wish to make use of this functionality through events dispatched by the application (synthetic events) can make use of the return value of the dispatchEvent() method:

if(obj.dispatchEvent(event)) {
  // event was not canceled, time for some magic
  …
}

When an event is dispatched to an object that participates in a tree (e.g. an element), it can reach event listeners on that object’s ancestors too. First all object’s ancestor event listeners whose capture variable is set to true are invoked, in tree order. Second, object’s own event listeners are invoked. And finally, and only if event’s bubbles attribute value is true, object’s ancestor event listeners are invoked again, but now in reverse tree order.

Lets look at an example of how events work in a tree:

<!doctype html><html>
 <head>
  <title>Boring example</title>
 </head>
 <body>
  <p>Hello <span id=x>world</span>!</p>
  <script>
   function test(e) {
     debug(e.target, e.currentTarget, e.eventPhase)
   }
   document.addEventListener("hey", test, {capture: true})
   document.body.addEventListener("hey", test)
   var ev = new Event("hey", {bubbles:true})
   document.getElementById("x").dispatchEvent(ev)
  </script>
 </body>
</html>

The debug function will be invoked twice. Each time the event’s target attribute value will be the span element. The first time currentTarget attribute’s value will be the document, the second time the body element. eventPhase attribute’s value switches from CAPTURING_PHASE to BUBBLING_PHASE. If an event listener was registered for the span element, eventPhase attribute’s value would have been AT_TARGET.

3.2. Interface Event

[Constructor(DOMString type, optional EventInit eventInitDict),
 Exposed=(Window,Worker)]

interface Event {
  readonly attribute DOMString type;
  readonly attribute EventTarget? target;
  readonly attribute EventTarget? currentTarget;

  const unsigned short NONE = 0;
  const unsigned short CAPTURING_PHASE = 1;
  const unsigned short AT_TARGET = 2;
  const unsigned short BUBBLING_PHASE = 3;
  readonly attribute unsigned short eventPhase;

  void stopPropagation();
  attribute boolean cancelBubble;
  void stopImmediatePropagation();

  readonly attribute boolean bubbles;
  readonly attribute boolean cancelable;
  void preventDefault();
  readonly attribute boolean defaultPrevented;

  [Unforgeable] readonly attribute boolean isTrusted;
  readonly attribute DOMTimeStamp timeStamp;

  void initEvent(DOMString type, optional boolean bubbles, optional boolean cancelable);
};

dictionary EventInit {
  boolean bubbles = false;
  boolean cancelable = false;
};

An Event object allows for signaling that something has occurred. e.g. that an image has completed downloading. It is represented by the Event interface or an interface that inherits from the Event interface.

event = new Event(type [, eventInitDict])

Returns a new event whose type attribute value is set to type. The optional eventInitDict argument allows for setting the bubbles and cancelable attributes via object members of the same name.

event . type

Returns the type of event, e.g. "click", "hashchange", or "submit".

event . target

Returns the object to which event is dispatched.

event . currentTarget

Returns the object whose event listener’s callback is currently being invoked.

event . eventPhase

Returns the event’s phase, which is one of NONE, CAPTURING_PHASE, AT_TARGET, and BUBBLING_PHASE.

event . stopPropagation()

When dispatched in a tree, invoking this method prevents event from reaching any objects other than the current object.

event . stopImmediatePropagation()

Invoking this method prevents event from reaching any registered event listeners after the current one finishes running and, when dispatched in a tree, also prevents event from reaching any other objects.

event . bubbles

Returns true or false depending on how event was initialized. True if event goes through its target attribute value’s ancestors in reverse tree order, and false otherwise.

event . cancelable

Returns true or false depending on how event was initialized. Its return value does not always carry meaning, but true can indicate that part of the operation during which event was dispatched, can be canceled by invoking the preventDefault() method.

event . preventDefault()

If invoked when the cancelable attribute value is true, and while executing a listener for the event with passive set to false, signals to the operation that caused event to be dispatched that it needs to be canceled.

event . defaultPrevented

Returns true if preventDefault() was invoked successfully to indicate cancellation, and false otherwise.

event . isTrusted

Returns true if event was dispatched by the user agent, and false otherwise.

event . timeStamp

Returns the creation time of event as the number of milliseconds that passed since 00:00:00 UTC on 1 January 1970.

The type attribute’s getter must return the value it was initialized to. When an event is created the attribute must be initialized to the empty string.

The target attribute’s getter and currentTarget attribute’s getter must return the values they were initialized to. When an event is created the attributes must be initialized to null.

The eventPhase attribute’s getter must return the value it was initialized to, which must be one of the following:

NONE (numeric value 0)

Events not currently dispatched are in this phase.

CAPTURING_PHASE (numeric value 1)

When an event is dispatched to an object that participates in a tree it will be in this phase before it reaches its target attribute value.

AT_TARGET (numeric value 2)

When an event is dispatched it will be in this phase on its target attribute value.

BUBBLING_PHASE (numeric value 3)

When an event is dispatched to an object that participates in a tree it will be in this phase after it reaches its target attribute value.

Initially the attribute must be initialized to NONE.

Each event has the following associated flags that are all initially unset:

• stop propagation flag
• stop immediate propagation flag
• canceled flag
• in passive listener flag
• initialized flag
• dispatch flag

The stopPropagation() method, when invoked, must set the context object’s stop propagation flag.

The cancelBubble attribute’s getter must return true if context object’s stop propagation flag is set, and false otherwise.

The cancelBubble attribute’s setter must set context object’s stop propagation flag if the given value is true, and do nothing otherwise.

The stopImmediatePropagation() method must set both the stop propagation flag and stop immediate propagation flag.

The bubbles and cancelable attributes must return the values they were initialized to.

The preventDefault() method, when invoked, must set the canceled flag if the cancelable attribute value is true and the in passive listener flag is unset.

This means there are scenarios where invoking preventDefault() has no effect. User agents are encouraged to log the precise cause in a developer console, to aid debugging.

The defaultPrevented attribute must return true if the canceled flag is set and false otherwise.

The isTrusted attribute’s getter must return the value it was initialized to. When an event is created the attribute must be initialized to false.

Note: isTrusted is a convenience that indicates whether an event is dispatched by the user agent (as opposed to using dispatchEvent()). The sole legacy exception is click(), which causes the user agent to dispatch an event whose isTrusted attribute is initialized to false.

The timeStamp attribute’s getter must return the value it was initialized to. When an event is created the attribute must be initialized to the number of milliseconds that have passed since 00:00:00 UTC on 1 January 1970, ignoring leap seconds.

To initialize an event, with type, bubbles, and cancelable, run these steps:

1. Set the initialized flag.

2. Unset the stop propagation flag, stop immediate propagation flag, and canceled flag.

3. Set the isTrusted attribute to false.

4. Set the target attribute to null.

5. Set the type attribute to type.

6. Set the bubbles attribute to bubbles.

7. Set the cancelable attribute to cancelable.

The initEvent(type, bubbles, cancelable) method, when invoked, must run these steps:

1. If context object’s dispatch flag is set, terminate these steps.

2. Initialize the context object with type, bubbles, and cancelable.

Note: As events have constructors initEvent() is superfluous. However, it has to be supported for legacy content.

3.3. Interface CustomEvent

[Constructor(DOMString type, optional CustomEventInit eventInitDict),
 Exposed=(Window,Worker)]
interface CustomEvent : Event {
  readonly attribute any detail;

  void initCustomEvent(DOMString type, optional boolean bubbles = false, optional boolean cancelable = false, optional any detail = null);
};

dictionary CustomEventInit : EventInit {
  any detail = null;
};

Events using the CustomEvent interface can be used to carry custom data.

event = new CustomEvent(type [, eventInitDict])

Works analogously to the constructor for Event except that the optional eventInitDict argument now allows for setting the detail attribute too.

event . detail

Returns any custom data event was created with. Typically used for synthetic events.

The detail attribute must return the value it was initialized to.

The initCustomEvent(type, bubbles, cancelable, detail) method, when invoked, must run these steps:

1. If context object’s dispatch flag is set, terminate these steps.
2. Initialize the context object with type, bubbles, and cancelable.
3. Set context object’s detail attribute to detail.

3.4. Constructing events

When a constructor of the Event interface, or of an interface that inherits from the Event interface, is invoked, these steps must be run:

1. Create an event that uses the interface the constructor was invoked upon.

2. Set its initialized flag.

3. Initialize the type attribute to the type argument.

4. If there is an eventInitDict argument then for each dictionary member present, find the attribute on event whose identifier matches the key of the dictionary member and then set the attribute to the value of that dictionary member.

5. Return the event.

To create an event using eventInterface, which must be either Event or an interface that inherits from it, and optionally given a Realm realm, run these steps:

1. Create a new object event using eventInterface. If realm is given, use that Realm; otherwise, use the default behavior defined in Web IDL.

2. Set event’s initialized flag.

3. Let defaultEventInitDict be the result of converting the JavaScript value undefined to the dictionary type accepted by eventInterface’s constructor. (This dictionary type will either be EventInit or a dictionary that inherits from it.)

4. For each dictionary member present in defaultEventInitDict, find the attribute on event whose identifier matches the key of the dictionary member and then set the attribute to the default value of that dictionary member.

5. Initialize event’s isTrusted attribute to true.

6. Return event.

3.5. Defining event interfaces

In general, when defining a new interface that inherits from Event please always ask feedback from the WHATWG or the W3C www-dom@w3.org mailing list.

The CustomEvent interface can be used as starting point. However, do not introduce any init*Event() methods as they are redundant with constructors. Interfaces that inherit from the Event interface that have such a method only have it for historical reasons.

3.6. Interface EventTarget

[Exposed=(Window,Worker)]
interface EventTarget {
  void addEventListener(DOMString type, EventListener? callback, optional (AddEventListenerOptions or boolean) options);
  void removeEventListener(DOMString type, EventListener? callback, optional (EventListenerOptions or boolean) options);
  boolean dispatchEvent(Event event);
};

callback interface EventListener {
  void handleEvent(Event event);
};

dictionary EventListenerOptions {
  boolean capture = false;
};

dictionary AddEventListenerOptions : EventListenerOptions {
  boolean passive = false;
  boolean once = false;
};

The EventTarget object represents the target to which an event is dispatched when something has occurred.

Each EventTarget object has an associated list of event listeners.

An event listener can be used to observe a specific event.

An event listener consists of these fields:

• type (a string)
• callback (an EventListener)
• capture (a boolean, initially false)
• passive (a boolean, initially false)
• once (a boolean, initially false)
• removed (a boolean for bookkeeping purposes, initially false)

Although callback is an EventListener, as can be seen from the fields above, an event listener is a broader concept.

Each EventTarget object also has an associated get the parent algorithm, which takes an event event, and returns an EventTarget object. Unless specified otherwise it returns null.

Nodes and documents override the get the parent algorithm.

Each EventTarget object can have an associated activation behavior algorithm. The activation behavior algorithm is passed an event, as indicated in the dispatch algorithm.

This exists because user agents perform certain actions for certain EventTarget objects, e.g., the area element, in response to synthetic MouseEvent events whose type attribute is click. Web compatibility prevented it from being removed and it is now the enshrined way of defining an activation of something. [HTML51]

Each EventTarget object that has activation behavior, can additionally have both (not either) a legacy-pre-activation behavior algorithm and a legacy-canceled-activation behavior algorithm.

These algorithms only exist for checkbox and radio input elements and are not to be used for anything else. [HTML51]

target . addEventListener(type, callback [, options])

Appends an event listener for events whose type attribute value is type. The callback argument sets the callback that will be invoked when the event is dispatched.

The options argument sets listener-specific options. For compatibility this can be just a boolean, in which case the method behaves exactly as if the value was specified as options’ capture member.

When set to true, options’ capture member prevents callback from being invoked when the event’s eventPhase attribute value is BUBBLING_PHASE. When false (or not present), callback will not be invoked when event’s eventPhase attribute value is CAPTURING_PHASE. Either way, callback will be invoked if event’s eventPhase attribute value is AT_TARGET.

When set to true, options’ passive member indicates that the callback will not cancel the event by invoking preventDefault(). This is used to enable performance optimizations described in §3.7 Observing event listeners.

When set to true, options’s once member indicates that the callback will only be invoked once after which the event listener will be removed.

The event listener is appended to target’s list of event listeners and is not appended if it is a duplicate, i.e., having the same type, callback, and capture values.

target . removeEventListener(type, callback [, options])

Remove the event listener in target’s list of event listeners with the same type, callback, and options.

target . dispatchEvent(event)

Dispatches a synthetic event event to target and returns true if either event’s cancelable attribute value is false or its preventDefault() method was not invoked, and false otherwise.

To flatten options, run these steps:

1. Let capture be false.

2. If options is a boolean, set capture to options.

3. If options is a dictionary, then set capture to options’s capture.

4. Return capture.

To flatten more options, run these steps:

1. Let capture be the result of flattening options.

2. Let once and passive be false.

3. If options is a dictionary, then set passive to options’s passive and once to options’s once.

4. Return capture, passive, and once.

The addEventListener(type, callback, options) method, when invoked, must run these steps:

1. If callback is null, then return.

2. Let capture, passive, and once be the result of flattening more options.

3. If context object’s associated list of event listener does not contain an event listener whose type is type, callback is callback, and capture is capture, then append a new event listener to it, whose type is type, callback is callback, capture is capture, passive is passive, and once is once.

The removeEventListener(type, callback, options) method, when invoked, must run these steps:

1. Let capture be the result of flattening options.

2. If there is an event listener in the associated list of event listeners whose type is type, callback is callback, and capture is capture, then set that event listener’s removed to true and remove it from the associated list of event listeners.

The dispatchEvent(event) method, when invoked, must run these steps:

1. If event’s dispatch flag is set, or if its initialized flag is not set, throw an "InvalidStateError" exception.[WEBIDL]

2. Initialize event’s isTrusted attribute to false.

3. Dispatch the event and return the value that returns.

3.7. Observing event listeners

In general, developers do not expect the presence of an event listener to be observable. The impact of an event listener is determined by its callback. That is, a developer adding a no-op event listener would not expect it to have any side effects.

Unfortunately, some event APIs have been designed such that implementing them efficiently requires observing event listeners. This can make the presence of listeners observable in that even empty listeners can have a dramatic performance impact on the behavior of the application. For example, touch and wheel events which can be used to block asynchronous scrolling. In some cases this problem can be mitigated by specifying the event to be cancelable only when there is at least one non-passive listener. For example, non-passive TouchEvent listeners must block scrolling, but if all listeners are passive then scrolling can be allowed to start in parallel by making the TouchEvent uncancelable (so that calls to preventDefault() are ignored). So code dispatching an event is able to observe the absence of non-passive listeners, and use that to clear the cancelable property of the event being dispatched.

Ideally, any new event APIs are defined such that they do not need this property (use public-script-coord@w3.org for discussion).

3.8. Dispatching events

To dispatch an event to a target, with an optional legacy target override flag, and an optional legacyOutputDidListenersThrowFlag, run these steps:

1. Set event’s dispatch flag.
2. Initialize event’s target attribute to target, if legacy target override flagis not given, and target’s associated Document otherwise. [HTML51]
3. If event’s target attribute value is participating in a tree, let event path be a static ordered list of all its ancestors in tree order, and let event path be the empty list otherwise.

4. Let isActivationEvent be true, if event is a MouseEvent object and event’s type attribute is "click", and false otherwise.

5. Let activationTarget be target, if isActivationEvent is true and target has activation behavior, and null otherwise.

6. Initialize event’s eventPhase attribute to CAPTURING_PHASE.

7. If activationTarget is non-null and activationTarget has legacy-pre-activation behavior, then run activationTarget’s legacy-pre-activation behavior.

8. For each object in event path, invoke its event listeners with event event, as long as event’s stop propagation flag is unset.
9. Initialize event’s eventPhase attribute to AT_TARGET.
10. Invoke the event listeners of event’s target attribute value with event, if event’s stop propagation flag is unset.
11. If event’s bubbles attribute value is true, run these substeps:

    1. Reverse the order of event path.

    2. Initialize event’s eventPhase attribute to BUBBLING_PHASE.

    3. For each object in event path, invoke its event listeners, with event event as long as event’s stop propagation flag is unset.

12. Unset event’s dispatch flag, stop propagation flag, and stop immediate propagation flag.
13. Set event’s eventPhase attribute to NONE.
14. Set event’s currentTarget attribute to null.

15. If activationTarget is non-null, then:

    1. If event’s canceled flag is unset, then run activationTarget’s activation behavior with event.

    2. Otherwise, if activationTarget has legacy-canceled-activation behavior, then run activationTarget’s legacy-canceled-activation behavior.

16. Return false if event’s canceled flag is set, and true otherwise.

To invoke an object with event and optional legacyOutputDidListenersThrowFlag, run these steps:

1. If event’s stop propagation flag is set, then return.

2. Let listeners be a copy of the event listeners associated with the object.
3. Initialize event’s currentTarget attribute to the object.
4. For each event listener in listeners, whose removed is false:

   1. Let listener be the event listener.

   2. If event’s type attribute value is not listener’s type, terminate these substeps (and run them for the next event listener).

   3. If event’s eventPhase attribute value is CAPTURING_PHASE and listener’s capture is false, terminate these substeps (and run them for the next event listener).

   4. If event’s eventPhase attribute value is BUBBLING_PHASE and listener’s capture is true, terminate these substeps (and run them for the next event listener).

   5. If listener’s once is true, then remove listener from object’s associated list of event listeners.

   6. If listener’s passive is true, then set event’s in passive listener flag.

   7. Call listener’s callback’s handleEvent, with the event passed to this algorithm as the first argument and event’s currentTarget attribute value as callback this value. If this throws any exception, report the exception.

      1. Report the exception.

      2. Set legacyOutputDidListenersThrowFlag if given.

         The legacyOutputDidListenersThrowFlag is only used by Indexed Database API. [INDEXEDDB]

   8. Unset event’s in passive listener flag.

   9. If event’s stop immediate propagation flag is set, then return found.

3.9. Action versus occurrence

An event signifies an occurrence, not an action. Phrased differently, it represents a notification from an algorithm and can be used to influence the future course of that algorithm (e.g., through invoking preventDefault()). Events must not be used as actions or initiators that cause some algorithm to start running. That is not what they are for.

This is called out here specifically because previous iterations of the DOM had a concept of "default actions" associated with events that gave folks all the wrong ideas. Events do not represent or cause actions, they can only be used to influence an ongoing one.

4. Nodes

4.1. Introduction to "The DOM"

In its original sense, "The DOM" is an API for accessing and manipulating documents (in particular, HTML and XML documents). In this specification, the term "document" is used for any markup-based resource, ranging from short static documents to long essays or reports with rich multimedia, as well as to fully-fledged interactive applications.

These documents are presented as a node tree. Some of the nodes in the tree can have children, while others are always leaves.

To illustrate, consider this HTML document:

<!DOCTYPE html>
<html class=e>
 <head><title>Aliens?</title></head>
 <body>Why yes.</body>
</html>

It is represented as follows:

• Document
  • Doctype: html
  • Element: html class="e"
    • Element: head
      • Element: title
        • Text: Aliens?
    • Text: ⏎␣
    • Element: body
      • Text: Why yes.⏎

Note that, due to the magic of HTML parser, not all ASCII whitespace were turned into Text nodes, but the general concept is clear. Markup goes in, a tree of nodes comes out.

Note: The most excellent Live DOM Viewer can be used to explore this matter in more detail.

4.2. Node tree

Objects implementing the Document, DocumentFragment, DocumentType, Element, Text, ProcessingInstruction, or Comment interface (simply called nodes) participate in a tree, simply named the node tree.

A node tree is constrained as follows, expressed as a relationship between the type of node and its allowed children:

Document

In tree order:

1. Zero or more nodes each of which is either ProcessingInstruction or Comment.

2. Optionally one DocumentType node.

3. Zero or more nodes each of which is either ProcessingInstruction or Comment.

4. Optionally one Element node.

5. Zero or more nodes each of which is either ProcessingInstruction or Comment.

DocumentFragment

Element

Zero or more nodes each of which is one of Element, ProcessingInstruction, Comment, or Text.

DocumentType

Text

ProcessingInstruction

Comment

None.

To determine the length of a node node, switch on node:

DocumentType

Zero.

Text

ProcessingInstruction

Comment

The number of code units in its data.

Any other node

Its number of children.

A node is considered empty if its length is zero.

4.2.1. Mutation algorithms

To ensure pre-insertion validity of a node into a parent before a child, run these steps:

1. If parent is not a Document, DocumentFragment, or Element node, throw a HierarchyRequestError.

2. If node is a host-including inclusive ancestor of parent, throw a HierarchyRequestError.

3. If child is not null and its parent is not parent, throw a NotFoundError.

4. If node is not a DocumentFragment, DocumentType, Element, Text, ProcessingInstruction, or Comment node, throw a HierarchyRequestError.

5. If either node is a Text node and parent is a document, or node is a doctype and parent is not a document, throw a HierarchyRequestError.

6. If parent is a document, and any of the statements below, switched on node, are true, throw a HierarchyRequestError.

   DocumentFragment node

   If node has more than one element child or has a Text node child.

   Otherwise, if node has one element child and either parent has an element child, child is a doctype, or child is not null and a doctype is following child.

   element

   parent has an element child, child is a doctype, or child is not null and a doctype is following child.

   doctype

   parent has a doctype child, child is non-null and an element is preceding child, or child is null and parent has an element child.

To pre-insert a node into a parent before a child, run these steps:

1. Ensure pre-insertion validity of node into parent before child.

2. Let reference child be child.

3. If reference child is node, set it to node’s next sibling.

4. Adopt node into parent’s node document.

5. Insert node into parent before reference child.

6. Return node.

Specifications may define insertion steps for all or some nodes. The algorithm is passed newNode, as indicated in the insert algorithm below.

To insert a node into a parent before a child with an optional suppress observers flag, run these steps:

1. Let count be the number of children of node if it is a DocumentFragment node, and one otherwise.

2. If child is non-null, run these substeps:

   1. For each range whose start node is parent and start offset is greater than child’s index, increase its start offset by count.

   2. For each range whose end node is parent and end offset is greater than child’s index, increase its end offset by count.

3. Let nodes be node’s children if node is a DocumentFragment node, and a list containing solely node otherwise.

4. If node is a DocumentFragment node, remove its children with the suppress observers flag set.

5. If node is a DocumentFragment node, queue a mutation record of "childList" for node with removedNodes nodes.

   Note: This step intentionally does not pay attention to the suppress observers flag.

6. For each newNode in nodes, in tree order, run these substeps:

   1. Insert newNode into parent before child or at the end of parent if child is null.

   2. Run the insertion steps with newNode.

   3. For each inclusive descendant inclusiveDescendant of node, in tree order, run the insertion steps with inclusiveDescendant and parent.

7. If suppress observers flag is unset, queue a mutation record of "childList" for parent with addedNodes nodes, nextSibling child, and previousSibling child’s previous sibling or parent’s last child if child is null.

To append a node to a parent, pre-insert node into parent before null.

To replace a child with node within a parent, run these steps:

1. If parent is not a Document, DocumentFragment, or Element node, throw a HierarchyRequestError.

2. If node is a host-including inclusive ancestor of parent, throw a HierarchyRequestError.

3. If child’s parent is not parent, throw a NotFoundError.

4. If node is not a DocumentFragment, DocumentType, Element, Text, ProcessingInstruction, or Comment node, throw a HierarchyRequestError.

5. If either node is a Text node and parent is a document, or node is a doctype and parent is not a document, throw a HierarchyRequestError.

6. If parent is a document, and any of the statements below, switched on node, are true, throw a HierarchyRequestError.

   DocumentFragment node

   If node has more than one element child or has a Text node child.

   Otherwise, if node has one element child and either parent has an element child that is not child or a doctype is following child.

   element

   parent has an element child that is not child or a doctype is following child.

   doctype

   parent has a doctype child that is not child, or an element is preceding child.

   Note: The above statements differ from the pre-insert algorithm.

7. Let reference child be child’s next sibling.

8. If reference child is node, set it to node’s next sibling.

9. Let previousSibling be child’s previous sibling.

10. Adopt node into parent’s node document.

11. Let removedNodes be the empty list.

12. If child’s parent is not null, run these substeps:

    1. Set removedNodes to a list solely containing child.

    2. Remove child from its parent with the suppress observers flag set.

    The above can only be false if child is node.

13. Let nodes be node’s children if node is a DocumentFragment node, and a list containing solely node otherwise.

14. Insert node into parent before reference child with the suppress observers flag set.

15. Queue a mutation record of "childList" for target parent with addedNodes nodes, removedNodes a list solely containing child, nextSibling reference child, and previousSibling previousSibling.

16. Return child.

To replace all with a node within a parent, run these steps:

1. If node is not null, adopt node into parent’s node document.

2. Let removedNodes be parent’s children.

3. Let addedNodes be the empty list if node is null, node’s children if node is a DocumentFragment node, and a list containing node otherwise.

4. Remove all parent’s children, in tree order, with the suppress observers flag set.

5. If node is not null, insert node into parent before null with the suppress observers flag set.

6. Queue a mutation record of "childList" for parent with addedNodes addedNodes and removedNodes removedNodes.

Note: This algorithm does not make any checks with regards to the node tree constraints. Specification authors need to use it wisely.

To pre-remove a child from a parent, run these steps:

1. If child’s parent is not parent, throw a NotFoundError.

2. Remove child from parent.

3. Return child.

Specifications may define removing steps for all or some nodes. The algorithm is passed removedNode, and optionally oldParent, as indicated in the remove algorithm below.

To remove a node from a parent with an optional suppress observers flag set, run these steps:

1. Let index be node’s index.

2. For each range whose start node is an inclusive descendant of node, set its start to (parent, index).

3. For each range whose end node is an inclusive descendant of node, set its end to (parent, index).

4. For each range whose start node is parent and start offset is greater than index, decrease its start offset by one.

5. For each range whose end node is parent and end offset is greater than index, decrease its end offset by one.

6. For each NodeIterator object iterator whose root’s node document is node’s node document, run the NodeIterator pre-removing steps given node and iterator.

7. Let oldPreviousSibling be node’s previous sibling.

8. Let oldNextSibling be node’s next sibling.

9. Remove node from its parent.

10. Run the removing steps with node and parent.

11. For each inclusive ancestor inclusiveAncestor of node, if inclusiveAncestor has any registered observers whose options' subtree is true, then for each such registered observer registered, append a transient registered observer whose observer and options are identical to those of registered and source which is registered to node’s list of registered observers.

12. If suppress observers flag is unset, queue a mutation record of "childList" for parent with removedNodes a list solely containing node, nextSibling oldNextSibling, and previousSibling oldPreviousSibling.

4.2.2. Interface NonElementParentNode

Web compatibility prevents the getElementById() method from being exposed on elements (and therefore on ParentNode).

[NoInterfaceObject,
 Exposed=Window]
interface NonElementParentNode {
  Element? getElementById(DOMString elementId);
};
Document implements NonElementParentNode;
DocumentFragment implements NonElementParentNode;

node . getElementById(elementId)

Returns the first element within node’s descendants whose ID is elementId.

The getElementById(elementId) method, when invoked, must return the first element, in tree order, within context object’s descendants, whose ID is elementId, and null if there is no such element otherwise.

4.2.3. Interface ParentNode

To convert nodes into a node, given nodes and document, run these steps:

1. Let node be null.
2. Replace each string in nodes with a new Text node whose data is the string and node document is document.
3. If nodes contains one node, set node to that node.
4. Otherwise, set node to a new DocumentFragment whose node document is document, and then append each node in nodes, if any, to it.
5. Return node.

[NoInterfaceObject,
 Exposed=Window]
interface ParentNode {
  [SameObject] readonly attribute HTMLCollection children;
  readonly attribute Element? firstElementChild;
  readonly attribute Element? lastElementChild;
  readonly attribute unsigned long childElementCount;

  [Unscopable] void prepend((Node or DOMString)... nodes);
  [Unscopable] void append((Node or DOMString)... nodes);

  Element? querySelector(DOMString selectors);
  [NewObject] NodeList querySelectorAll(DOMString selectors);
};
Document implements ParentNode;
DocumentFragment implements ParentNode;
Element implements ParentNode;

collection = node . children

Returns the child elements.

element = node . firstElementChild

Returns the first child that is an element, and null otherwise.

element = node . lastElementChild

Returns the last child that is an element, and null otherwise.

node . prepend(nodes)

Inserts nodes before the first child of node, while replacing strings in nodes with equivalent Text nodes.

Throws a HierarchyRequestError if the constraints of the node tree are violated.

node . append(nodes)

Inserts nodes after the last child of node, while replacing strings in nodes with equivalent Text nodes.

Throws a HierarchyRequestError if the constraints of the node tree are violated.

node . querySelector(selectors)

Returns the first element that is a descendant of node that matches selectors.

node . querySelectorAll(selectors)

Returns all element descendants of node that match selectors.

The children attribute’s getter must return an HTMLCollection collection rooted at the context object matching only element children.

The firstElementChild attribute’s getter must return the first child that is an element, and null otherwise.

The lastElementChild attribute’s getter must return the last child that is an element, and null otherwise.

The childElementCount attribute’s getter must return the number of children of the context object that are elements.

The prepend(nodes) method, when invoked, must run these steps:

1. Let node be the result of converting nodes into a node given nodes and context object’s node document.

2. Pre-insert node into context object before the context object’s first child.

The append(nodes) method, when invoked, must run these steps:

1. Let node be the result of converting nodes into a node given nodes and context object’s node document.

2. Append node to context object.

The querySelector(selectors) method, when invoked, must return the first result of running scope-match a selectors string selectors against the context object, and null if the result is an empty list otherwise.

The querySelectorAll(selectors) method, when invoked, must return the static result of running scope-match a selectors string selectors against the context object.

4.2.4. Interface NonDocumentTypeChildNode

Web compatibility prevents the previousElementSibling and nextElementSibling attributes from being exposed on doctypes (and therefore on ChildNode).

[NoInterfaceObject,
 Exposed=Window]
interface NonDocumentTypeChildNode {
  readonly attribute Element? previousElementSibling;
  readonly attribute Element? nextElementSibling;
};
Element implements NonDocumentTypeChildNode;
CharacterData implements NonDocumentTypeChildNode;

element = node . previousElementSibling

Returns the first preceding sibling that is an element, and null otherwise.

element = node . nextElementSibling

Returns the first following sibling that is an element, and null otherwise.

The previousElementSibling attribute’s getter must return the first preceding sibling that is an element, and null otherwise.

The nextElementSibling attribute’s getter must return the first following sibling that is an element, and null otherwise.

4.2.5. Interface ChildNode

[NoInterfaceObject,
 Exposed=Window]
interface ChildNode {
  [Unscopable] void before((Node or DOMString)... nodes);
  [Unscopable] void after((Node or DOMString)... nodes);
  [Unscopable] void replaceWith((Node or DOMString)... nodes);
  [Unscopable] void remove();
};
DocumentType implements ChildNode;
Element implements ChildNode;
CharacterData implements ChildNode;

node . before(nodes)

Inserts nodes just before node, while replacing strings in nodes with equivalent Text nodes.

Throws a HierarchyRequestError if the constraints of the node tree are violated.

node . after(nodes)

Inserts nodes just after node, while replacing strings in nodes with equivalent Text nodes.

Throws a HierarchyRequestError if the constraints of the node tree are violated.

node . replaceWith(nodes)

Replaces node with nodes, while replacing strings in nodes with equivalent Text nodes.

Throws a HierarchyRequestError if the constraints of the node tree are violated.

node . remove()

Removes node.

The before(nodes) method, when invoked, must run these steps:

1. Let parent be context object’s parent.

2. If parent is null, then return.

3. Let viablePreviousSibling be context object’s first preceding sibling not in nodes, and null otherwise.

4. Let node be the result of converting nodes into a node, given nodes and context object’s node document.

5. If viablePreviousSibling is null, set it to parent’s first child, and to viablePreviousSibling’s next sibling otherwise.

6. Pre-insert node into parent before viablePreviousSibling.

The after(nodes) method, when invoked, must run these steps:

1. Let parent be context object’s parent.

2. If parent is null, then return.

3. Let viableNextSibling be context object’s first following sibling not in nodes, and null otherwise.

4. Let node be the result of converting nodes into a node, given nodes and context object’s node document.

5. Pre-insert node into parent before viableNextSibling.

The replaceWith(nodes) method, when invoked, must run these steps:

1. Let parent be context object’s parent.

2. If parent is null, then return.

3. Let viableNextSibling be context object’s first following sibling not in nodes, and null otherwise.

4. Let node be the result of converting nodes into a node, given nodes and context object’s node document.

5. If context object’s parent is parent, replace the context object with node within parent.

   Context object could have been inserted into node.

6. Otherwise, pre-insert node into parent before viableNextSibling.

The remove() method, when invoked, must run these steps:

1. If the context object does not have a parent, terminate these steps.

2. Remove the context object from the context object’s parent.

4.2.6. Old-style collections: NodeList and HTMLCollection

A collection is an object that represents a lists of DOM nodes. A collection can be either live or static. Unless otherwise stated, a collection must be live.

If a collection is live, then the attributes and methods on that object must operate on the actual underlying data, not a snapshot of the data.

When a collection is created, a filter and a root are associated with it.

The collection then represents a view of the subtree rooted at the collection’s root, containing only nodes that match the given filter. The view is linear. In the absence of specific requirements to the contrary, the nodes within the collection must be sorted in tree order.

4.2.6.1. Interface NodeList

A NodeList object is a collection of nodes.

[Exposed=Window]
interface NodeList {
  getter Node? item(unsigned long index);
  readonly attribute unsigned long length;
  iterable<Node>;
};

collection . length

Returns the number of nodes in the collection.

element = collection . item(index)

element = collection[index]

Returns the node with index index from the collection. The nodes are sorted in tree order.

4.2.6.2. Interface HTMLCollection

[Exposed=Window]
interface HTMLCollection {
  readonly attribute unsigned long length;
  getter Element? item(unsigned long index);
  getter Element? namedItem(DOMString name);
};

An HTMLCollection object is a collection of elements.

Note: HTMLCollection is an historical artifact we cannot rid the web of. While developers are of course welcome to keep using it, new API standard designers ought not to use it (use sequence<T> in IDL instead).

collection . length

Returns the number of elements in the collection.

element = collection . item(index)

element = collection[index]

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

element = collection . namedItem(name)

element = collection[name]

Returns the first element with ID or name namefrom the collection.

4.3. Mutation observers

Each unit of related similar-origin browsing contexts has a mutation observer compound microtask queued flag, which is initially unset, and an associated list of MutationObserver objects, which is initially empty.

To queue a mutation observer compound microtask, run these steps:

1. If mutation observer compound microtask queued flag is set, terminate these steps.

2. Set mutation observer compound microtask queued flag.

3. Queue a compound microtask to notify mutation observers.

To notify mutation observers, run these steps:

1. Unset mutation observer compound microtask queued flag.

2. Let notify list be a copy of unit of related similar-origin browsing contexts' list of MutationObserver objects.

3. For each MutationObserver object mo in notify list, execute a compound microtask subtask to run these steps:

   1. Let queue be a copy of mo’s record queue.

   2. Empty mo’s record queue.

   3. Remove all transient registered observers whose observer is mo.

   4. If queue is non-empty, call mo’s callback with queue as first argument, and mo (itself) as second argument and callback this value. If this throws an exception, report the exception.

Each node has an associated list of registered observers.

A registered observer consists of an observer (a MutationObserver object) and options (a MutationObserverInit dictionary). A transient registered observer is a specific type of registered observer that has a source which is a registered observer.

Transient registered observers are used to track mutations within a given node’s descendants after node has been removed so they do not get lost when subtree is set to true on node’s parent.

4.3.1. Interface MutationObserver

[Constructor(MutationCallback callback)]
interface MutationObserver {
  void observe(Node target, optional MutationObserverInit options);
  void disconnect();
  sequence<MutationRecord> takeRecords();
};

callback MutationCallback = void (sequence<MutationRecord> mutations, MutationObserver observer);

dictionary MutationObserverInit {
  boolean childList = false;
  boolean attributes;
  boolean characterData;
  boolean subtree = false;
  boolean attributeOldValue;
  boolean characterDataOldValue;
  sequence<DOMString> attributeFilter;
};

A MutationObserver object can be used to observe mutations to the tree of nodes.

Each MutationObserver object has these associated concepts:

• A callback set on creation.

• A list of nodes on which it is a registered observer’s observer that is initially empty.

• A list of MutationRecord objects called the record queue that is initially empty.

observer = new MutationObserver(callback)

Constructs a MutationObserver object and sets its callback to callback. The callback is invoked with a list of MutationRecord objects as first argument and the constructed MutationObserver object as second argument. It is invoked after nodes registered with the observe() method, are mutated.

observer . observe(target, options)

Instructs the user agent to observe a given target (a node) and report any mutations based on the criteria given by options (an object).

The options argument allows for setting mutation observation options via object members. These are the object members that can be used:

childList

Set to true if mutations to target’s children are to be observed.

attributes

Set to true if mutations to target’s attributes are to be observed. Can be omitted if attributeOldValue and/or attributeFilter is specified.

{{MutationObserverInit/characterData

Set to true if mutations to target’s data are to be observed. Can be omitted if characterDataOldValue is specified.

subtree

Set to true if mutations to not just target, but also target’s descendants are to be observed.

attributeOldValue

Set to true if attributes is true or omitted and target’s attribute value before the mutation needs to be recorded.

characterDataOldValue

Set to true if characterData is set to true or omitted and target’s data before the mutation needs to be recorded.

attributeFilter

Set to a list of attribute local names (without namespace) if not all attribute mutations need to be observed and attributes is true or omitted.

observer . disconnect()

Stops observer from observing any mutations. Until the observe() method is used again, observer’s callback will not be invoked.

observer . takeRecords()

Empties the record queue and returns what was in there.

The MutationObserver(callback) constructor must create a new MutationObserver object with callback set to callback, append it to the unit of related similar-origin browsing contexts' list of MutationObserver objects, and then return it.

The observe(target, options) method, when invoked, must run these steps:

1. If either options’ attributeOldValue or attributeFilter is present and options’ attributes is omitted, set options’ attributes to true.

2. If options’ characterDataOldValue is present and options’ characterData is omitted, set options’ characterData to true.

3. If none of options’ childList, attributes, and characterData is true, throw a TypeError.

4. If options’ attributeOldValue is true and options’ attributes is false, throw a JavaScript TypeError.

5. If options’ attributeFilter is present and options’ attributes is false, throw a JavaScript TypeError.

6. If options’ characterDataOldValue is true and options’ characterData is false, throw a JavaScript TypeError.

7. For each registered observer registered in target’s list of registered observers whose observer is the context object:

   1. Remove all transient registered observers whose source is registered.

   2. Replace registered’s options with options.

8. Otherwise, add a new registered observer to target’s list of registered observers with the context object as the observer and options as the options, and add target to context object’s list of nodes on which it is registered.

The disconnect() method, when invoked, must, for each node node in the context object’s list of nodes, remove any registered observer on node for which the context object is the observer, and also empty context object’s record queue.

The takeRecords() method, when invoked, must return a copy of the record queue and then empty the record queue.

4.3.2. Queuing a mutation record

To queue a mutation record of type for target with one or more of (depends on type) name name, namespace namespace, oldValue oldValue, addedNodes addedNodes, removedNodes removedNodes, previousSibling previousSibling, and nextSibling nextSibling, run these steps:

1. Let interested observers be an initially empty set of MutationObserver objects optionally paired with a string.

2. Let nodes be the inclusive ancestors of target.

3. Then, for each node in nodes, and then for each registered observer (with registered observer’s options as options) in node’s list of registered observers, run these substeps:

   1. If none of the following are true

      • node is not target and options’ subtree is false
      • type is "attributes" and options’ attributes is false
      • type is "attributes", options’ attributeFilter is present, and options’ attributeFilter does not contain name or namespace is non-null
      • type is "characterData" and options’ characterData is false
      • type is "childList" and options’ childList is false

      then run these subsubsteps:

      1. If registered observer’s observer is not in interested observers, append registered observer’s observer to interested observers.

      2. If either type is "attributes" and options’ attributeOldValue is true, or type is "characterData" and options’ characterDataOldValue is true, set the paired string of registered observer’s observer in interested observers to oldValue.

4. Then, for each observer in interested observers:

   1. Let record be a new MutationRecord object with its type set to type and target set to target.

   2. If name and namespace are given, set record’s attributeName to name, and record’s attributeNamespace to namespace.

   3. If addedNodes is given, set record’s addedNodes to addedNodes.

   4. If removedNodes is given, set record’s removedNodes to removedNodes,

   5. If previousSibling is given, set record’s previousSibling to previousSibling.

   6. If nextSibling is given, set record’s nextSibling to nextSibling.

   7. If observer has a paired string, set record’s oldValue to observer’s paired string.

   8. Append record to observer’s record queue.

5. Queue a mutation observer compound microtask.

4.3.3. Interface MutationRecord

[Exposed=Window]
interface MutationRecord {
  readonly attribute DOMString type;
  [SameObject] readonly attribute Node target;
  [SameObject] readonly attribute NodeList addedNodes;
  [SameObject] readonly attribute NodeList removedNodes;

  readonly attribute Node? previousSibling;
  readonly attribute Node? nextSibling;

  readonly attribute DOMString? attributeName;
  readonly attribute DOMString? attributeNamespace;
  readonly attribute DOMString? oldValue;
};

record . type

Returns "attributes" if it was an attribute mutation. "characterData" if it was a mutation to a CharacterData node. And "childList" if it was a mutation to the tree of nodes.

record . target

Returns the node the mutation affected, depending on the type. For "attributes", it is the element whose attribute changed. For "characterData", it is the CharacterData node. For "childList", it is the node whose children changed.

record . addedNodes

record . removedNodes

Return the nodes added and removed respectively.

record . previousSibling

record . nextSibling

Return the previous and next sibling respectively of the added or removed nodes, and null otherwise.

record . attributeName

Returns the local name of the changed attribute, and null otherwise.

record . attributeNamespace

Returns the namespace of the changed attribute, and null otherwise.

record . oldValue

The return value depends on type. For "attributes", it is the value of the changed attribute before the change. For "characterData", it is the data of the changed node before the change. For "childList", it is null.

The type attribute’s getter and target attribute’s getter must return the values they were initialized to.

The addedNodes attribute’s getter and removedNodes attribute’s getter must return the values they were initialized to. Unless stated otherwise, when a MutationRecord object is created, they must both be initialized to an empty NodeList.

The previousSibling attribute’s getter, nextSibling attribute’s getter, attributeName attribute’s gettr, attributeNamespace attribute’s getter, and oldValue attribute’s getter must return the values they were initialized to. Unless stated otherwise, when a MutationRecord object is created, they must be initialized to null.

4.3.4. Garbage collection

Nodes have a strong reference to registered observers in their list of registered observers.

Registered observers in a node’s list of registered observers have a weak reference to the node.

4.4. Interface Node

[Exposed=Window]
interface Node : EventTarget {
  const unsigned short ELEMENT_NODE = 1;
  const unsigned short ATTRIBUTE_NODE = 2;
  const unsigned short TEXT_NODE = 3;
  const unsigned short CDATA_SECTION_NODE = 4;
  const unsigned short ENTITY_REFERENCE_NODE = 5; // historical
  const unsigned short ENTITY_NODE = 6; // historical
  const unsigned short PROCESSING_INSTRUCTION_NODE = 7;
  const unsigned short COMMENT_NODE = 8;
  const unsigned short DOCUMENT_NODE = 9;
  const unsigned short DOCUMENT_TYPE_NODE = 10;
  const unsigned short DOCUMENT_FRAGMENT_NODE = 11;
  const unsigned short NOTATION_NODE = 12; // historical
  readonly attribute unsigned short nodeType;
  readonly attribute DOMString nodeName;

  readonly attribute USVString baseURI;

  readonly attribute Document? ownerDocument;
  readonly attribute Node? parentNode;
  readonly attribute Element? parentElement;
  boolean hasChildNodes();
  [SameObject] readonly attribute NodeList childNodes;
  readonly attribute Node? firstChild;
  readonly attribute Node? lastChild;
  readonly attribute Node? previousSibling;
  readonly attribute Node? nextSibling;

  attribute DOMString? nodeValue;
  attribute DOMString? textContent;
  void normalize();

  [NewObject] Node cloneNode(optional boolean deep = false);
  boolean isEqualNode(Node? other);

  const unsigned short DOCUMENT_POSITION_DISCONNECTED = 0x01;
  const unsigned short DOCUMENT_POSITION_PRECEDING = 0x02;
  const unsigned short DOCUMENT_POSITION_FOLLOWING = 0x04;
  const unsigned short DOCUMENT_POSITION_CONTAINS = 0x08;
  const unsigned short DOCUMENT_POSITION_CONTAINED_BY = 0x10;
  const unsigned short DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC = 0x20;
  unsigned short compareDocumentPosition(Node other);
  boolean contains(Node? other);

  DOMString? lookupPrefix(DOMString? namespace);
  DOMString? lookupNamespaceURI(DOMString? prefix);
  boolean isDefaultNamespace(DOMString? namespace);

  Node insertBefore(Node node, Node? child);
  Node appendChild(Node node);
  Node replaceChild(Node node, Node child);
  Node removeChild(Node child);
};

Note: Node is an abstract interface and does not exist as node. It is used by all nodes (Document, DocumentFragment, DocumentType, Element, Text, ProcessingInstruction, and Comment).

Each node has an associated node document, set upon creation, that is a document.

Note: A node’s node document can be changed by the adopt algorithm.

node . nodeType

Returns the type of node, represented by a number from the following list:

Node . ELEMENT_NODE (1)

node is an element.

Node . ATTRIBUTE_NODE (2)

node is an attribute.

Node . TEXT_NODE (3)

node is a Text node.

Node . CDATA_SECTION_NODE (4)

node is a CDATASection node.

Node . PROCESSING_INSTRUCTION_NODE (7)

node is a ProcessingInstruction node.

Node . COMMENT_NODE (8)

node is a Comment node.

Node . DOCUMENT_NODE (9)

node is a document.

Node . DOCUMENT_TYPE_NODE (10)

node is a doctype.

Node . DOCUMENT_FRAGMENT_NODE (11)

node is a DocumentFragment node.

node . nodeName

Returns a string appropriate for the type of node, as follows:

Element

Its tagName attribute value.

Attr

Its qualified name.

Text

"#text".

CDATASection

"#cdata-section".

ProcessingInstruction

Its target.

Comment

"#comment".

Document

"#document".

DocumentType

Its name.

DocumentFragment

"#document-fragment".

The nodeType attribute’s getter, when invoked, must return the first matching statement, switching on the context object:

Element

ELEMENT_NODE (1);

Attr

ATTRIBUTE_NODE (2);

Text

TEXT_NODE (3);

CDATASection

CDATA_SECTION_NODE (4);

ProcessingInstruction

PROCESSING_INSTRUCTION_NODE (7);

Comment

COMMENT_NODE (8);

Document

DOCUMENT_NODE (9);

DocumentType

DOCUMENT_TYPE_NODE (10);

DocumentFragment

DOCUMENT_FRAGMENT_NODE (11).

The nodeName attribute’s getter must return the first matching statement, switching on the context object:

Element

Its tagName attribute value.

Attr

Its qualified name.

Text

"#text".

CDATASection

"#cdata-section".

ProcessingInstruction

Its target.

Comment

"#comment".

Document

"#document".

DocumentType

Its name.

DocumentFragment

"#document-fragment".

node . baseURI

Returns node’s node document’s document base URL.

The baseURI attribute’s getter must return node document’s document base URL.

node . ownerDocument

Returns the node document.

Returns null for documents.

node . parentNode

Returns the parent.

node . parentElement

Returns the parent element.

node . hasChildNodes()

Returns whether node has children.

node . childNodes

Returns the children.

node . firstChild

Returns the first child.

node . lastChild

Returns the last child.

node . previousSibling

Returns the previous sibling.

node . nextSibling

Returns the next sibling.

The nodeValue attribute’s getter must return the following, depending on the context object:

Attr

context object’s value.

Text

Comment

ProcessingInstruction

The context object’s data.

Any other node

Null.

The nodeValue attribute’s setter must, if the new value is null, act as if it was the empty string instead, and then do as described below, depending on the context object:

Attr

Set an existing attribute value with context object and new value.

Text

Comment

ProcessingInstruction

Replace data with node context object, offset 0, count context object’s length, and data new value.

Any other node

Do nothing.

The textContent attribute’s getter must return the following, depending on the context object:

DocumentFragment

Element

The concatenation of data of all the Text node descendants of the context object, in tree order.

Attr

context object’s value.

Text

ProcessingInstruction

Comment

The context object’s data.

Any other node

Null.

The textContent attribute’s setter must, if the new value is null, act as if it was the empty string instead, and then do as described below, depending on the context object:

DocumentFragment

Element

1. Let node be null.

2. If new value is not the empty string, set node to a new Text node whose data is new value.

3. Replace all with node within the context object.

Attr

Set an existing attribute value with context object and new value.

Text

ProcessingInstruction

Comment

Replace data with node context object, offset 0, count context object’s length, and data new value.

Any other node

Do nothing.

node . normalize()

Removes empty exclusive Text nodes and concatenates the data of remaining contiguous exclusive Text nodes into the first of their nodes.

The normalize() method, when invoked, must run these steps for each descendant exclusive Text node node of context object:

1. Let length be node’s length.
2. If length is zero, then remove node and continue with the next exclusive Text node, if any.
3. Let data be the concatenation of the data of node’s contiguous exclusive Text nodes (excluding itself), in tree order.
4. Replace data with node node, offset length, count 0, and data data.
5. Let currentNode be node’s next sibling.

6. While currentNode is an exclusive Text node:

   1. For each range whose start node is currentNode, add length to its start offset and set its start node to node.

   2. For each range whose end node is currentNode, add length to its end offset and set its end node to node.

   3. For each range whose start node is currentNode’s parent and start offset is currentNode’s index, set its start node to node and its start offset to length.

   4. For each range whose end node is currentNode’s parent and end offset is currentNode’s index, set its end node to node and its end offset to length.

   5. Add currentNode’s length to length.

   6. Set currentNode to its next sibling.

7. Remove node’s contiguous exclusive Text nodes (excluding itself), in tree order.

node . cloneNode([deep = false])

Returns a copy of node. If deep is true, the copy also includes the node’s descendants.

node . isEqualNode(other)

Returns whether node and other have the same properties.

node . compareDocumentPosition(other)

Returns a bitmask indicating the position of other relative to node. These are the bits that can be set:

Node . DOCUMENT_POSITION_DISCONNECTED (1)

Set when node and other are not in the same tree.

Node . DOCUMENT_POSITION_PRECEDING (2)

Set when other is preceding node.

Node . DOCUMENT_POSITION_FOLLOWING (4)

Set when other is following node.

Node . DOCUMENT_POSITION_CONTAINS (8)

Set when other is an ancestor of node.

Node . DOCUMENT_POSITION_CONTAINED_BY (16, 10 in hexadecimal)

Set when other is a descendant of node.

node . contains(other)

Returns true if other is an inclusive descendant of node, and false otherwise.

These are the constants compareDocumentPosition() returns as mask:

• DOCUMENT_POSITION_DISCONNECTED (1);
• DOCUMENT_POSITION_PRECEDING (2);
• DOCUMENT_POSITION_FOLLOWING (4);
• DOCUMENT_POSITION_CONTAINS (8);
• DOCUMENT_POSITION_CONTAINED_BY (16, 10 in hexadecimal);
• DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC (32, 20 in hexadecimal).

The compareDocumentPosition(other) method, when invoked, must run these steps:

1. If context object is other, then return zero.

2. Let node1 be other and node2 be context object.

3. Let attr1 and attr2 be null.

4. If node1 is an attribute, then set attr1 to node1 and node1 to attr1’s element.

5. If node2 is an attribute, then:

   1. Set attr2 to node2 and node2 to attr2’s element.

   2. If attr1 and node1 are non-null, and node2 is node1, then:

      1. For each attribute attr in node2’s attribute list:

         1. If attr equals attr1, then return the result of adding DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC and DOCUMENT_POSITION_PRECEDING.

         2. If attr equals attr2, then return the result of adding DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC and DOCUMENT_POSITION_FOLLOWING.

6. If node1 or node2 is null, or node1’s root is not node2’s root, then return the result of adding DOCUMENT_POSITION_DISCONNECTED, DOCUMENT_POSITION_IMPLEMENTATION_SPECIFIC, and either DOCUMENT_POSITION_PRECEDING or DOCUMENT_POSITION_FOLLOWING, with the constraint that this is to be consistent, together.

   Whether to return DOCUMENT_POSITION_PRECEDING or DOCUMENT_POSITION_FOLLOWING is typically implemented via pointer comparison. In JavaScript implementations a cached Math.random() value can be used.

7. If node1 is an ancestor of node2 and attr1 is null, or node1 is node2 and attr2 is non-null, then return the result of adding DOCUMENT_POSITION_CONTAINS to DOCUMENT_POSITION_PRECEDING.

8. If node1 is a descendant of node2 and attr2 is null, or node1 is node2 and attr1 is non-null, then return the result of adding DOCUMENT_POSITION_CONTAINED_BY to DOCUMENT_POSITION_FOLLOWING.

9. If node1 is preceding node2, then return DOCUMENT_POSITION_PRECEDING.

   Due to the way attributes are handled in this algorithm this results in a node’s attributes counting as preceding that node’s children, despite attributes not participating in a tree.

10. Return DOCUMENT_POSITION_FOLLOWING.

The contains(other) method, when invoked, must return true if other is an inclusive descendant of context object, and false otherwise (including when other is null).

To locate a namespace prefix for an element using namespace, run these steps:

1. If element’s namespace is namespace and its namespace prefix is not null, then return its namespace prefix.

2. If element has an attribute whose namespace prefix is "xmlns" and value is namespace, then return element’s first such attribute’s local name.

3. If element’s parent element is not null, then return the result of running locate a namespace prefix on that element using namespace.

4. Return null.

To locate a namespace for a node using prefix switch on node:

Element

1. If its namespace is not null and its namespace prefix is prefix, then return namespace.

2. If it has an attribute whose namespace is the XMLNS namespace, namespace prefix is "xmlns", and local name is prefix, or if prefix is null and it has an attribute whose namespace is the XMLNS namespace, namespace prefix is null, and local name is "xmlns", then return its value if it is not the empty string, and null otherwise.

3. If its parent element is null, then return null.

4. Return the result of running locate a namespace on its parent element using prefix.

Document

1. If its document element is null, then return null.

2. Return the result of running locate a namespace on its document element using prefix.

DocumentType

DocumentFragment

Return null.

Attr

1. If its element is null, then return null.

2. Return the result of running locate a namespace on its element using prefix.

Any other node

1. If its parent element is null, then return null.

2. Return the result of running locate a namespace on its parent element using prefix.

The lookupPrefix(namespace) method, when invoked, must run these steps:

1. If namespace is null or the empty string, then return null.

2. Switch on the context object:

   Element

   Return the result of locating a namespace prefix for it using namespace.

   Document

   Return the result of locating a namespace prefix for its document element, if its document element is non-null, and null otherwise.

   DocumentType

   DocumentFragment

   Return null.

   Attr

   Return the result of locating a namespace prefix for its element, if its element is non-null, and null otherwise.

   Any other node

   Return the result of locating a namespace prefix for its parent element, if its parent element is non-null, and null otherwise.

The lookupNamespaceURI(prefix) method, when invoked, must run these steps:

1. If prefix is the empty string, then set it to null.

2. Return the result of running locate a namespace for the context object using prefix.

The isDefaultNamespace(namespace) method, when invoked, must run these steps:

1. If namespace is the empty string, then set it to null.

2. Let defaultNamespace be the result of running locate a namespace for context object using null.

3. Return true if defaultNamespace is the same as namespace, and false otherwise.

The insertBefore(node, child) method, when invoked, must return the result of pre-inserting node into context object before child.

The appendChild(node) method, when invoked, must return the result of appending node to context object.

The replaceChild(node, child) method, when invoked, must return the result of replacing child with node within context object.

The removeChild(child) method, when invoked, must return the result of pre-removing child from context object.

The list of elements with local name localName for a node root is the HTMLCollection returned by the following algorithm:

1. If localName is "*" (U+002A), return a HTMLCollection rooted at root, whose filter matches only elements.

2. Otherwise, if root’s node document is an HTML document, return a HTMLCollection rooted at root, whose filter matches the following descendant elements:

   • Whose namespace is the HTML namespace and whose local name is localName converted to ASCII lowercase.
   • Whose namespace is not the HTML namespace and whose local name is localName.

3. Otherwise, return a HTMLCollection rooted at root, whose filter matches descendant elements whose local name is localName.

When invoked with the same argument, and as long as root’s node document’s type has not changed, the same HTMLCollection object may be returned as returned by an earlier call.

The list of elements with namespace namespace and local name localName for a node root is the HTMLCollection returned by the following algorithm:

1. If namespace is the empty string, set it to null.

2. If both namespace and localName are "*" (U+002A), return a HTMLCollection rooted at root, whose filter matches descendant elements.

3. Otherwise, if namespace is "*" (U+002A), return a HTMLCollection rooted at root, whose filter matches descendant elements whose local name is localName.

4. Otherwise, if localName is "*" (U+002A), return a HTMLCollection rooted at root, whose filter matches descendant elements whose namespace is namespace.

5. Otherwise, return a HTMLCollection rooted at root, whose filter matches descendant elements whose namespace is namespace and local name is localName.

When invoked with the same arguments, the same HTMLCollection object may be returned as returned by an earlier call.

The list of elements with class names classNames for a node root is the HTMLCollection returned by the following algorithm:

1. Let classes be the result of running the ordered set parser on classNames.

2. If classes is the empty set, return an empty HTMLCollection.

3. Return a HTMLCollection rooted at root, whose filter matches descendant elements that have all their classes in classes.

   The comparisons for the classes must be done in an ASCII case-insensitive manner if root’s node document’s mode is "quirks", and in a case-sensitive manner otherwise.

When invoked with the same argument, the same HTMLCollection object may be returned as returned by an earlier call.

4.5. Interface Document

[Constructor,
 Exposed=Window]
interface Document : Node {
  [SameObject] readonly attribute DOMImplementation implementation;
  readonly attribute USVString URL;
  readonly attribute USVString documentURI;
  readonly attribute USVString origin;
  readonly attribute DOMString compatMode;
  readonly attribute DOMString characterSet;
  readonly attribute DOMString charset; // for legacy use, alias of .characterSet
  readonly attribute DOMString inputEncoding; // for legacy use, alias of .characterSet
  readonly attribute DOMString contentType;

  readonly attribute DocumentType? doctype;
  readonly attribute Element? documentElement;
  HTMLCollection getElementsByTagName(DOMString localName);
  HTMLCollection getElementsByTagNameNS(DOMString? namespace, DOMString localName);
  HTMLCollection getElementsByClassName(DOMString classNames);

  [NewObject] Element createElement(DOMString localName);
  [NewObject] Element createElementNS(DOMString? namespace, DOMString qualifiedName);
  [NewObject] DocumentFragment createDocumentFragment();
  [NewObject] Text createTextNode(DOMString data);
  [NewObject] CDATASection createCDATASection(DOMString data);
  [NewObject] Comment createComment(DOMString data);
  [NewObject] ProcessingInstruction createProcessingInstruction(DOMString target, DOMString data);

  [NewObject] Node importNode(Node node, optional boolean deep = false);
  Node adoptNode(Node node);

  [NewObject] Attr createAttribute(DOMString localName);
  [NewObject] Attr createAttributeNS(DOMString? namespace, DOMString qualifiedName);

  [NewObject] Event createEvent(DOMString interface);

  [NewObject] Range createRange();

  // NodeFilter.SHOW_ALL = 0xFFFFFFFF
  [NewObject] NodeIterator createNodeIterator(Node root, optional unsigned long whatToShow = 0xFFFFFFFF, optional NodeFilter? filter = null);
  [NewObject] TreeWalker createTreeWalker(Node root, optional unsigned long whatToShow = 0xFFFFFFFF, optional NodeFilter? filter = null);
};

[Exposed=Window]
interface XMLDocument : Document {};

Document nodes are simply known as documents.

Each document has an associated encoding (an encoding), content type (a string), URL (a URL), origin (an origin), type ("xml" or "html"), and mode ("no-quirks", "quirks", or "limited-quirks"). [ENCODING] [URL] [HTML51]

Unless stated otherwise, a document’s encoding is the utf-8 encoding, its content type is "application/xml", its URL is "about:blank", origin is an opaque origin, type is "xml", and its mode is "no-quirks".

A document is said to be an XML document if its type is "xml", and an HTML document otherwise. Whether a document is an HTML document or an XML document affects the behavior of certain APIs.

A document is said to be in no-quirks mode if its mode is "no-quirks", quirks mode if its mode is "quirks", and limited-quirks mode if its mode is "limited-quirks".

document = new Document()

Returns a new document.

document . implementation

Returns document’s DOMImplementation object.

document . URL

document . documentURI

Returns document’s URL.

document . origin

Returns document’s origin.

document . compatMode

Returns the string "BackCompat" if document’s mode is "quirks mode", and "CSS1Compat" otherwise.

document . characterSet

Returns document’s encoding.

document . contentType

Returns document’s content type.

The Document() constructor must return a new document whose origin is the origin of the global object’s associated document. [HTML51]

Note: Unlike createDocument(), this constructor does not return an XMLDocument object, but a document (Document object).

The implementation attribute’s getter must return the DOMImplementation object that is associated with the document.

The URL’s getter and documentURI attribute’s getter must return the URL.

The origin attribute’s getter must return the Unicode serialization of context object’s origin.

The compatMode attribute’s getter must return "BackCompat" if the context object’s mode is "quirks", and "CSS1Compat" otherwise.

The characterSet attribute’s getter, charSet attribute’s getter, and inputEncoding attribute’s getter, must return context object’s encoding’s name.

The contentType attribute’s getter must return the content type.

document . doctype

Returns the doctype or null if there is none.

document . documentElement

Returns the document element.

collection = document . getElementsByTagName(localName)

If localName is "*" returns a HTMLCollection of all descendant elements.

Otherwise, returns a HTMLCollection of all descendant elements whose local name is localName. (Matches case-insensitively against elements in the HTML namespace within an HTML document.)

collection = document . getElementsByTagNameNS(namespace, localName)

If namespace and localName are "*" returns a HTMLCollection of all descendant elements.

If only namespace is "*" returns a HTMLCollection of all descendant elements whose local name is localName.

If only localName is "*" returns a HTMLCollection of all descendant elements whose namespace is namespace.

Otherwise, returns a HTMLCollection of all descendant elements whose namespace is namespace and local name is localName.

collection = document . getElementsByClassName(classNames)

collection = element . getElementsByClassName(classNames)

Returns a HTMLCollection of the elements in the object on which the method was invoked (a document or an element) that have all the classes given by classes.

The classes argument is interpreted as a space-separated list of classes.

The doctype attribute’s getter must return the child of the document that is a doctype, and null otherwise.

The documentElement attribute’s getter must return the document element.

The getElementsByTagName(localName) method, when invoked, must return the list of elements with local name localName for the context object.

Note: Thus, in an HTML document, document.getElementsByTagName("FOO") will match FOO elements that are not in the HTML namespace, and foo elements that are in the HTML namespace, but not FOO elements that are in the HTML namespace.

The getElementsByTagNameNS(namespace, localName) method, when invoked, must return the list of elements with namespace namespace and local name localName for the context object.

The getElementsByClassName(classNames) method, when invoked, must return the list of elements with class names classNames for the context object.

<div id="example">  <p id="p1" class="aaa bbb"/>
  <p id="p2" class="aaa ccc"/>
  <p id="p3" class="bbb ccc"/>
</div>

element = document . createElement(localName)

Returns an element in the HTML namespace [see bug 19431] with localName as local name. (In an HTML document localName is lowercased.)

element = document . createElement(localName)

element = document . createElementNS(namespace, qualifiedName)

Returns an element with namespace namespace. Its namespace prefix will be everything before ":" (U+003E) in qualifiedName or null. Its local name will be everything after ":" (U+003E) in qualifiedName or qualifiedName.

If localName does not match the Name production an InvalidCharacterError will be thrown.

If one of the following conditions is true a NamespaceError will be thrown:

• localName does not match the QName production.
• Namespace prefix is not null and namespace is the empty string.
• Namespace prefix is "xml" and namespace is not the XML namespace.
• qualifiedName or namespace prefix is "xmlns" and namespace is not the XMLNS namespace.
• namespace is the XMLNS namespace and neither qualifiedName nor namespace prefix is "xmlns".

documentFragment = document . createDocumentFragment()

Returns a DocumentFragment node.

text = document . createTextNode(data)

Returns a Text node whose data is data.

cdataSection = document . createCDATASection(data)

Returns a CDATASection node whose data is data.

comment = document . createComment(data)

Returns a Comment node whose data is data.

processingInstruction = document . createProcessingInstruction(target, data)

Returns a ProcessingInstruction node whose target is target and data is data.

If target does not match the Name production an InvalidCharacterError will be thrown.

If data contains "?>" an InvalidCharacterError will be thrown.

The element interface for any name and namespace is Element, unless stated otherwise.

Note: The HTML Standard will e.g. define that for html and the HTML namespace, the HTMLHtmlElement interface is used. [[!HTML5]

The createElement(localName) method, when invoked, must run the these steps:

1. If localName does not match the Name production, throw an InvalidCharacterError.

2. If the context object is an HTML document, let localName be converted to ASCII lowercase.

3. Let interface be the element interface for localName and the HTML namespace.

4. Return a new element that implements interface, with no attributes, namespace set to the HTML namespace [see bug 19431], local name set to localName, and node document set to the context object.

The createElementNS(namespace, qualifiedName) method, when invoked, must run these steps:

1. Let namespace, prefix, and localName be the result of passing namespace and qualifiedName to validate and extract. Rethrow any exceptions.

2. Let interface be the element interface for localName and namespace.

3. Return a new element that implements interface, with no attributes, namespace set to namespace, namespace prefix set to prefix, local name set to localName, and node document set to the context object.

The createDocumentFragment() method, when invoked, must return a new DocumentFragment node with its node document set to the context object.

The createTextNode(data) method, when invoked, must return a new Text node with its data set to data and node document set to the context object.

Note: No check is performed that data consists of characters that match the Char production.

The createCDATASection(data) method, when invoked, must run these steps:

1. If context object is an HTML document, then throw a NotSupportedError.

2. If data contains the string "]]>", then throw an InvalidCharacterError.

3. Return a new CDATASection node with its data set to data and node document set to the context object.

The createComment(data) method, when invoked, must return a new Comment node with its data set to data and node document set to the context object.

Note: No check is performed that data consists of characters that match the Char production or that it contains two adjacent hyphens or ends with a hyphen.

The createProcessingInstruction(target, data) method, when invoked, must run these steps:

1. If target does not match the Name production, throw an InvalidCharacterError.

2. If data contains the string "?>", throw an InvalidCharacterError.

3. Return a new ProcessingInstruction node, with target set to target, data set to data, and node document set to the context object.

Note: No check is performed that target contains "xml" or ":", or that data contains characters that match the Char production.

clone = document . importNode(node [, deep = false])

Returns a copy of node. If deep is true, the copy also includes the node’s descendants.

If node is a document throws a NotSupportedError.

node = document . adoptNode(node)

Moves node from another document and returns it.

If node is a document throws a NotSupportedError.

The importNode(node, deep) method, when invoked, must run these steps:

1. If node is a document, throw a NotSupportedError.

2. Return a clone of node, with context object and the clone children flag set if deep is true.

Specifications may define adopting steps for all or some nodes. The algorithm is passed node and oldDocument, as indicated in the adopt algorithm.

To adopt a node into a document, run these steps:

1. Let oldDocument be node’s node document.

2. If node’s parent is not null, remove node from its parent.

3. If document is not the same as oldDocument, run these substeps:

   1. For each inclusiveDescendant in node’s inclusive descendants, run these subsubsteps:

      1. Set inclusiveDescendant’s node document to document.

      2. If inclusiveDescendant is an element, then set the node document of each attribute in inclusiveDescendant’s attribute list to document.

   2. For each inclusiveDescendant in node’s inclusive descendants, in tree order, run the adopting steps with inclusiveDescendant and oldDocument.

The adoptNode(node) method, when invoked, must run these steps:

1. If node is a document, throw a NotSupportedError.

2. Adopt node into the context object.

3. Return node.

The createAttribute(localName) method, when invoked, must run these steps:

1. If localName does not match the Name production in XML, then throw an InvalidCharacterError.

2. If the context object is an HTML document, then set localName to localName in ASCII lowercase.
3. Return a new attribute whose local name is localName and node document is context object.

The createAttributeNS(namespace, qualifiedName) method, when invoked, must run these steps:

1. Let namespace, prefix, and localName be the result of passing namespace and qualifiedName to validate and extract.

2. Return a new attribute whose namespace is namespace, namespace prefix is prefix, local name is localName, and node document is context object.

The createEvent(interface) method, when invoked, must run these steps:

1. Let constructor be null.

2. If interface is an ASCII case-insensitive match for any of the strings in the first column in the following table, then set constructor to the interface in the second column on the same row as the matching string:

   String	Interface	Notes
   "compositionevent"	CompositionEvent	[UIEVENTS]
   "customevent"	CustomEvent
   "event"	Event
   "event"	Event
   "events"	Event
   "hashchangeevent"	HashChangeEvent	[HTML51]
   "htmlevents"	Event
   "keyboardevent"	KeyboardEvent	[UIEVENTS]
   "messageevent"	MessageEvent	[WEBMESSAGING]
   "mouseevent"	MouseEvent	[UIEVENTS]
   "mouseevents"	MouseEvent	[UIEVENTS]
   "storageevent"	StorageEvent	[WEBSTORAGE]
   "uievent"	UIEvent	[UIEVENTS]
   "uievents"	UIEvent	[UIEVENTS]

3. If constructor is null, throw a NotSupportedError.

4. If the interface indicated by constructor is not exposed on the relevant global object of the context object, then throw a NotSupportedError.

   Typically user agents disable support for touch events in some configurations, in which case this clause would be triggered for the interface TouchEvent.

5. Let event be the result of creating an event given constructor.

6. Initialize event’s type attribute to the empty string.

7. Initialize event’s isTrusted attribute to false.

8. Unset event’s initialized flag.

9. Return event.

Note: Event constructors ought to be used instead.

The createRange() method, when invoked, must return a new range with (context object, 0) as its start and end.

Note: The Range() constructor ought to be used instead.

The createNodeIterator(root, whatToShow, filter) method, when invoked, must run these steps:

1. Create a NodeIterator object.

2. Set root to root and initialize the referenceNode attribute to the root argument.

3. Initialize the pointerBeforeReferenceNode attribute to true.

4. Set whatToShow to the whatToShow argument.

5. Set filter to filter.

6. Return the newly created NodeIterator object.

The createTreeWalker(root, whatToShow, filter) method, when invoked, must run these steps:

1. Create a TreeWalker object.

2. Set root to root and initialize the currentNode attribute to the root argument.

3. Set whatToShow to the whatToShow argument.

4. Set filter to filter.

5. Return the newly created TreeWalker object.

4.5.1. Interface DOMImplementation

User agents must create a DOMImplementation object whenever a document is created and associate it with that document.

[Exposed=Window]
interface DOMImplementation {
  [NewObject] DocumentType createDocumentType(DOMString qualifiedName, DOMString publicId, DOMString systemId);
  [NewObject] XMLDocument createDocument(DOMString? namespace, [TreatNullAs=EmptyString] DOMString qualifiedName, optional DocumentType? doctype = null);
  [NewObject] Document createHTMLDocument(optional DOMString title);

  boolean hasFeature(); // useless; always returns true
};

doctype = document . implementation . createDocumentType(qualifiedName, publicId, systemId)

Returns a doctype, with the given qualifiedName, publicId, and systemId. If qualifiedName does not match the Name production, an InvalidCharacterError is thrown, and if it does not match the QName production, a NamespaceError is thrown.

doc = document . implementation . createDocument(namespace, qualifiedName [, doctype = null])

Returns an XMLDocument [see bug 22960], with a document element whose local name is qualifiedName and whose namespace is namespace (unless qualifiedName is the empty string), and with doctype, if it is given, as its doctype.

This method throws the same exceptions as the createElementNS() method, when invoked with the same arguments.

doc = document . implementation . createHTMLDocument(title)

Returns a document, with a basic tree already constructed including a title element, unless the title argument is omitted.

4.6. Interface DocumentFragment

[Constructor,
 Exposed=Window]
interface DocumentFragment : Node {
};

A DocumentFragment node can have an associated element named host.

An object A is a host-including inclusive ancestor of an object B, if either A is an inclusive ancestor of B, or if B’s root has an associated host and A is a host-including inclusive ancestor of B’s root’s host.

Note: The DocumentFragment node’s host concept is useful for HTML’s template element and impacts the pre-insert and replace algorithms.

tree = new DocumentFragment()

Returns a new DocumentFragment node.

The DocumentFragment() constructor must return a new DocumentFragment node whose node document is current global object’s associated Document.

4.7. Interface DocumentType

[Exposed=Window]
interface DocumentType : Node {
  readonly attribute DOMString name;
  readonly attribute DOMString publicId;
  readonly attribute DOMString systemId;
};

DocumentType nodes are simply known as doctypes.

Doctypes have an associated name, public ID, and system ID.

When a doctype is created, its name is always given. Unless explicitly given when a doctype is created, its public ID and system ID are the empty string.

The name attribute’s getter must return the context object’s name.

The publicId attribute’s getter must return the context object’s public ID.

The systemId attribute’s getter must return the context object’s system ID.

4.8. Interface Element

[Exposed=Window]
interface Element : Node {
  readonly attribute DOMString? namespaceURI;
  readonly attribute DOMString? prefix;
  readonly attribute DOMString localName;
  readonly attribute DOMString tagName;

           attribute DOMString id;
           attribute DOMString className;
  [SameObject] readonly attribute DOMTokenList classList;

  boolean hasAttributes();
  [SameObject] readonly attribute NamedNodeMap attributes;
  DOMString? getAttribute(DOMString qualifiedName);
  DOMString? getAttributeNS(DOMString? namespace, DOMString localName);
  void setAttribute(DOMString qualifiedName, DOMString value);
  void setAttributeNS(DOMString? namespace, DOMString qualifiedName, DOMString value);
  void removeAttribute(DOMString qualifiedName);
  void removeAttributeNS(DOMString? namespace, DOMString localName);
  boolean hasAttribute(DOMString qualifiedName);
  boolean hasAttributeNS(DOMString? namespace, DOMString localName);

  Attr? getAttributeNode(DOMString qualifiedName);
  Attr? getAttributeNodeNS(DOMString? namespace, DOMString localName);
  Attr? setAttributeNode(Attr attr);
  Attr? setAttributeNodeNS(Attr attr);
  Attr removeAttributeNode(Attr attr);

  Element? closest(DOMString selectors);
  boolean matches(DOMString selectors);
  boolean webkitMatchesSelector(DOMString selectors); // historical alias of .matches

  HTMLCollection getElementsByTagName(DOMString localName);
  HTMLCollection getElementsByTagNameNS(DOMString? namespace, DOMString localName);
  HTMLCollection getElementsByClassName(DOMString classNames);

  Element? insertAdjacentElement(DOMString where, Element element); // historical
  void insertAdjacentText(DOMString where, DOMString data); // historical
};