Document Object Model Events (original) (raw)

Editors

Tom Pixley, Netscape Communications Corp.

Table of contents

1.1. Overview of the DOM Level 2 Event Model

The DOM Level 2 Event Model is designed with two main goals. The first goal is the design of a generic event system which allows registration of event handlers, describes event flow through a tree structure, and provides basic contextual information for each event. Additionally, the specification will provide standard modules of events for user interface control and document mutation notifications, including defined contextual information for each of these event modules.

The second goal of the event model is to provide a common subset of the current event systems used in DOM Level 0browsers. This is intended to foster interoperability of existing scripts and content. It is not expected that this goal will be met with full backwards compatibility. However, the specification attempts to achieve this when possible.

The following sections of the Event Model specification define both the specification for the DOM Event Model and a number of conformant event modules designed for use within the model. The Event Model consists of the two sections on event propagation and event listener registration and the Event interface.

A DOM application may use the hasFeature(feature, version) method of the DOMImplementationinterface with parameter values "Events" and "2.0" (respectively) to determine whether or not the event module is supported by the implementation. In order to fully support this module, an implementation must also support the "Core" feature defined in the DOM Level 2 Core specification [DOM Level 2 Core]. Please, refer to additional information about conformance in the DOM Level 2 Core specification [DOM Level 2 Core].

Each event module describes its own feature string in the event module listing.

1.1.1. Terminology

UI events

User interface events. These events are generated by user interaction through an external device (mouse, keyboard, etc.)

UI Logical events

Device independent user interface events such as focus change messages or element triggering notifications.

Mutation events

Events caused by any action which modifies the structure of the document.

Capturing

The process by which an event can be handled by one of the event's target's ancestors before being handled by the event's target.

Bubbling

The process by which an event propagates upward through its ancestors after being handled by the event's target.

Cancelable

A designation for events which indicates that upon handling the event the client may choose to prevent the DOM implementation from processing any default action associated with the event.

1.2. Description of event flow

Event flow is the process through which the an event originates from the DOM implementation and is passed into the Document Object Model. The methods of event capture and event bubbling, along with various event listener registration techniques, allow the event to then be handled in a number of ways. It can be handled locally at the EventTarget level or centrally from an EventTargethigher in the document tree.

1.2.1. Basic event flow

Each event has an EventTargettoward which the event is directed by the DOM implementation. ThisEventTargetis specified in the Event'starget attribute. When the event reaches the target, any event listeners registered on the EventTargetare triggered. Although all EventListenerson the EventTargetare guaranteed to be triggered by any event which is received by that EventTarget, no specification is made as to the order in which they will receive the event with regards to the other EventListenerson the EventTarget. If neither event capture or event bubbling are in use for that particular event, the event flow process will complete after all listeners have been triggered. If event capture or event bubbling is in use, the event flow will be modified as described in the sections below.

Any exceptions thrown inside an EventListenerwill not stop propagation of the event. It will continue processing any additional EventListenerin the described manner.

It is expected that actions taken by EventListeners may cause additional events to fire. Additional events should be handled in a synchronous manner and may cause reentrancy into the event model.

1.2.2. Event capture

Event capture is the process by which an EventListener registered on an ancestor of the event's target can intercept events of a given type before they are received by the event's target. Capture operates from the top of the tree, generally the Document, downward, making it the symmetrical opposite of bubbling which is described below. The chain of EventTargets from the top of the tree to the event's target is determined before the initial dispatch of the event. If modifications occur to the tree during event processing, event flow will proceed based on the initial state of the tree.

An EventListenerbeing registered on an EventTargetmay choose to have that EventListenercapture events by specifying the useCapture parameter of the addEventListener method to betrue. Thereafter, when an event of the given type is dispatched toward a descendant of the capturing object, the event will trigger any capturing event listeners of the appropriate type which exist in the direct line between the top of the document and the event's target. This downward propagation continues until the event's target is reached. A capturing EventListenerwill not be triggered by events dispatched directly to the EventTargetupon which it is registered.

If the capturing EventListenerwishes to prevent further processing of the event from occurring it may call the stopProgagation method of the Event interface. This will prevent further dispatch of the event, although additional EventListenersregistered at the same hierarchy level will still receive the event. Once an event's stopPropagation method has been called, further calls to that method have no additional effect. If no additional capturers exist and stopPropagation has not been called, the event triggers the appropriate EventListenerson the target itself.

Although event capture is similar to the delegation based event model in which all interested parties register their listeners directly on the target about which they wish to receive notifications, it is different in two important respects. First, event capture only allows interception of events which are targeted at descendantsof the capturing EventTarget. It does not allow interception of events targeted to the capturer'sancestors, its siblings, or its sibling's descendants. Secondly, event capture is not specified for a single EventTarget, it is specified for a specific type of event. Once specified, event capture intercepts all events of the specified type targeted toward any of the capturer's descendants.

1.2.3. Event bubbling

Events which are designated as bubbling will initially proceed with the same event flow as non-bubbling events. The event is dispatched to its target EventTargetand any event listeners found there are triggered. Bubbling events will then trigger any additional event listeners found by following the EventTarget's parent chain upward, checking for any event listeners registered on each successive EventTarget. This upward propagation will continue up to and including theDocument. EventListeners registered as capturers will not be triggered during this phase. The chain of EventTargets from the event target to the top of the tree is determined before the initial dispatch of the event. If modifications occur to the tree during event processing, event flow will proceed based on the initial state of the tree.

Any event handler may choose to prevent further event propagation by calling the stopPropagation method of the Eventinterface. If any EventListenercalls this method, all additional EventListenerson the current EventTargetwill be triggered but bubbling will cease at that level. Only one call to stopPropagation is required to prevent further bubbling.

1.2.4. Event cancelation

Some events are specified as cancelable. For these events, the DOM implementation generally has a default action associated with the event. An example of this is a hyperlink in a web browser. When the user clicks on the hyperlink the default action is generally to active that hyperlink. Before processing these events, the implementation must check for event listeners registered to receive the event and dispatch the event to those listeners. These listeners then have the option of canceling the implementation's default action or allowing the default action to proceed. In the case of the hyperlink in the browser, canceling the action would have the result of not activating the hyperlink.

Cancelation is accomplished by calling the Event'spreventDefault method. If one or more EventListenerscall preventDefault during any phase of event flow the default action will be canceled.

Different implementations will specify their own default actions, if any, associated with each event. The DOM does not attempt to specify these actions.

1.3. Event listener registration

1.3.1. Event registration interfaces

Interface EventTarget (introduced in DOM Level 2)

The EventTarget interface is implemented by allNodes in an implementation which supports the DOM Event Model. Therefore, this interface can be obtained by using binding-specific casting methods on an instance of theNode interface. The interface allows registration and removal of EventListenerson an EventTarget and dispatch of events to thatEventTarget.

IDL Definition

// Introduced in DOM Level 2: interface EventTarget { void addEventListener(in DOMString type, in EventListener listener, in boolean useCapture); void removeEventListener(in DOMString type, in EventListener listener, in boolean useCapture); boolean dispatchEvent(in Event evt) raises(EventException); };

Methods

addEventListener

This method allows the registration of event listeners on the event target. If an EventListeneris added to an EventTarget while it is processing an event, it will not be triggered by the current actions but may be triggered during a later stage of event flow, such as the bubbling phase.
If multiple identical EventListeners are registered on the same EventTarget with the same parameters the duplicate instances are discarded. They do not cause the EventListenerto be called twice and since they are discarded they do not need to be removed with the removeEventListener method.

Parameters

type of typeDOMString

The event type for which the user is registering

listener of type EventListener

The listener parameter takes an interface implemented by the user which contains the methods to be called when the event occurs.

useCapture of typeboolean

If true, useCapture indicates that the user wishes to initiate capture. After initiating capture, all events of the specified type will be dispatched to the registered EventListenerbefore being dispatched to any EventTargets beneath them in the tree. Events which are bubbling upward through the tree will not trigger an EventListenerdesignated to use capture.

No Return Value

No Exceptions

dispatchEvent

This method allows the dispatch of events into the implementations event model. Events dispatched in this manner will have the same capturing and bubbling behavior as events dispatched directly by the implementation. The target of the event is the EventTarget on which dispatchEventis called.

Parameters

evt of type Event

Specifies the event type, behavior, and contextual information to be used in processing the event.

Return Value

boolean The return value of dispatchEvent indicates whether any of the listeners which handled the event calledpreventDefault. If preventDefault was called the value is false, else the value is true.

Exceptions

EventException UNSPECIFIED_EVENT_TYPE_ERR: Raised if the Event's type was not specified by initializing the event beforedispatchEvent was called. Specification of the Event's type asnull or an empty string will also trigger this exception.

removeEventListener

This method allows the removal of event listeners from the event target. If an EventListeneris removed from an EventTarget while it is processing an event, it will not be triggered by the current actions. EventListeners can never be invoked after being removed.
Calling removeEventListener with arguments which do not identify any currently registered EventListeneron the EventTarget has no effect.

Parameters

type of typeDOMString

Specifies the event type of the EventListenerbeing removed.

listener of type EventListener

The EventListenerparameter indicates the EventListener to be removed.

useCapture of typeboolean

Specifies whether the EventListenerbeing removed was registered as a capturing listener or not. If a listener was registered twice, one with capture and one without, each must be removed separately. Removal of a capturing listener does not affect a non-capturing version of the same listener, and vice versa.

No Return Value

No Exceptions

Interface EventListener (introduced in DOM Level 2)

The EventListener interface is the primary method for handling events. Users implement the EventListenerinterface and register their listener on an EventTargetusing the AddEventListener method. The users should also remove their EventListener from its EventTargetafter they have completed using the listener.

When a Node is copied using thecloneNode method the EventListeners attached to the source Node are not attached to the copied Node. If the user wishes the sameEventListeners to be added to the newly created copy the user must add them manually.

IDL Definition

// Introduced in DOM Level 2: interface EventListener { void handleEvent(in Event evt); };

Methods

handleEvent

This method is called whenever an event occurs of the type for which the EventListener interface was registered.

Parameters

evt of type Event

The Event contains contextual information about the event. It also contains thestopPropagation and preventDefaultmethods which are used in determining the event's flow and default action.

No Return Value

No Exceptions

1.3.2. Interaction with HTML 4.0 event listeners

In HTML 4.0, event listeners were specified as attributes of an element. As such, registration of a second event listener of the same type would replace the first listener. The DOM Event Model allows registration of multiple event listeners on a single EventTarget. To achieve this, event listeners are no longer stored as attribute values.

In order to achieve compatibility with HTML 4.0, implementors may view the setting of attributes which represent event handlers as the creation and registration of an EventListeneron the EventTarget. The value of useCapture defaults tofalse. This EventListenerbehaves in the same manner as any other EventListenerswhich may be registered on the EventTarget. If the attribute representing the event listener is changed, this may be viewed as the removal of the previously registered EventListenerand the registration of a new one. No technique is provided to allow HTML 4.0 event listeners access to the context information defined for each event.

1.4. Event interface

Interface Event (introduced in DOM Level 2)

The Event interface is used to provide contextual information about an event to the handler processing the event. An object which implements the Event interface is generally passed as the first parameter to an event handler. More specific context information is passed to event handlers by deriving additional interfaces from Event which contain information directly relating to the type of event they accompany. These derived interfaces are also implemented by the object passed to the event listener.

IDL Definition

// Introduced in DOM Level 2: interface Event {

// PhaseType const unsigned short CAPTURING_PHASE = 1; const unsigned short AT_TARGET = 2; const unsigned short BUBBLING_PHASE = 3;

readonly attribute DOMString type; readonly attribute EventTarget target; readonly attribute EventTarget currentTarget; readonly attribute unsigned short eventPhase; readonly attribute boolean bubbles; readonly attribute boolean cancelable; readonly attribute DOMTimeStamp timeStamp; void stopPropagation(); void preventDefault(); void initEvent(in DOMString eventTypeArg, in boolean canBubbleArg, in boolean cancelableArg); };

Definition group PhaseType

An integer indicating which phase of event flow is being processed.

Defined Constants

AT_TARGET

The event is currently being evaluated at the target EventTarget.

BUBBLING_PHASE

The current event phase is the bubbling phase.

CAPTURING_PHASE

The current event phase is the capturing phase.

Attributes

bubbles of typeboolean, readonly

Used to indicate whether or not an event is a bubbling event. If the event can bubble the value is true, else the value is false.

cancelable of typeboolean, readonly

Used to indicate whether or not an event can have its default action prevented. If the default action can be prevented the value is true, else the value is false.

currentTarget of typeEventTarget, readonly

Used to indicate the EventTargetwhose EventListenersare currently being processed. This is particularly useful during capturing and bubbling.

eventPhase of typeunsigned short, readonly

Used to indicate which phase of event flow is currently being evaluated.

target of type EventTarget, readonly

Used to indicate the EventTargetto which the event was originally dispatched.

timeStamp of typeDOMTimeStamp, readonly

Used to specify the time (in milliseconds relative to the epoch) at which the event was created. Due to the fact that some systems may not provide this information the value oftimeStamp may be not available for all events. When not available, a value of 0 will be returned. Examples of epoch time are the time of the system start or 0:0:0 UTC 1st January 1970.

type of typeDOMString, readonly

The name of the event (case-insensitive). The name must be anXML name.

Methods

initEvent

The initEvent method is used to initialize the value of an Event created through theDocumentEventinterface. This method may only be called before theEvent has been dispatched via thedispatchEvent method, though it may be called multiple times during that phase if necessary. If called multiple times the final invocation takes precedence. If called from a subclass ofEvent interface only the values specified in theinitEvent method are modified, all other attributes are left unchanged.

Parameters

eventTypeArg of typeDOMString

Specifies the event type. This type may be any event type currently defined in this specification or a new event type.. The string must be an XML name.
Any new event type must not begin with any upper, lower, or mixed case version of the string "DOM". This prefix is reserved for future DOM event sets. It is also strongly recommended that third parties adding their own events use their own prefix to avoid confusion and lessen the probability of conflicts with other new events.

canBubbleArg of typeboolean

Specifies whether or not the event can bubble.

cancelableArg of typeboolean

Specifies whether or not the event's default action can be prevented.

No Return Value

No Exceptions

preventDefault

If an event is cancelable, thepreventDefault method is used to signify that the event is to be canceled, meaning any default action normally taken by the implementation as a result of the event will not occur. If, during any stage of event flow, the preventDefaultmethod is called the event is canceled. Any default action associated with the event will not occur. Calling this method for a non-cancelable event has no effect. OncepreventDefault has been called it will remain in effect throughout the remainder of the event's propagation. This method may be used during any stage of event flow.

No Parameters

No Return Value

No Exceptions

stopPropagation

The stopPropagation method is used prevent further propagation of an event during event flow. If this method is called by any EventListenerthe event will cease propagating through the tree. The event will complete dispatch to all listeners on the current EventTargetbefore event flow stops. This method may be used during any stage of event flow.

No Parameters

No Return Value

No Exceptions

Exception EventException introduced in DOM Level 2

Event operations may throw an EventExceptionas specified in their method descriptions.

IDL Definition

// Introduced in DOM Level 2: exception EventException { unsigned short code; }; // EventExceptionCode const unsigned short UNSPECIFIED_EVENT_TYPE_ERR = 0;

Definition group EventExceptionCode

An integer indicating the type of error generated.

Defined Constants

UNSPECIFIED_EVENT_TYPE_ERR

If the Event's type was not specified by initializing the event before the method was called. Specification of the Event's type as null or an empty string will also trigger this exception.

1.5. DocumentEvent interface

Interface DocumentEvent (introduced in DOM Level 2)

The DocumentEvent interface provides a mechanism by which the user can create an Event of a type supported by the implementation. It is expected that the DocumentEventinterface will be implemented on the same object which implements the Document interface in an implementation which supports the Event model.

IDL Definition

// Introduced in DOM Level 2: interface DocumentEvent { Event createEvent(in DOMString eventType) raises(DOMException); };

Methods

createEvent

Parameters

eventType of typeDOMString

The eventType parameter specifies the type of Event interface to be created. If the Event interface specified is supported by the implementation this method will return a new Event of the interface type requested. If the Event is to be dispatched via the dispatchEvent method the appropriate event init method must be called after creation in order to initialize the Event's values. As an example, a user wishing to synthesize some kind of UIEvent would call createEvent with the parameter "UIEvents". TheinitUIEvent method could then be called on the newly created UIEvent to set the specific type of UIEvent to be dispatched and set its context information.
The createEvent method is used in creating Events when it is either inconvenient or unnecessary for the user to create an Event themselves. In cases where the implementation provided Event is insufficient, users may supply their own Eventimplementations for use with the dispatchEventmethod.

Exceptions

DOMException NOT_SUPPORTED_ERR: Raised if the implementation does not support the type of Event interface requested

1.6. Event module definitions

The DOM Level 2 Event Model allows a DOM implementation to support multiple modules of events. The model has been designed to allow addition of new event modules as is required. The DOM will not attempt to define all possible events. For purposes of interoperability, the DOM will define a module of user interface events including lower level device dependent events, a module of UI logical events, and a module of document mutation events. Any new event types defined by third parties must not begin with any upper, lower, or mixed case version of the string "DOM". This prefix is reserved for future DOM event modules. It is also strongly recommended that third parties adding their own events use their own prefix to avoid confusion and lessen the probability of conflicts with other new events.

1.6.1. User Interface event types

The User Interface event module is composed of events listed in HTML 4.0 and additional events which are supported in DOM Level 0browsers.

A DOM application may use the hasFeature(feature, version) method of the DOMImplementationinterface with parameter values "UIEvents" and "2.0" (respectively) to determine whether or not the User Interface event module is supported by the implementation. In order to fully support this module, an implementation must also support the "Events" feature defined in this specification and the "Views" feature defined in the DOM Level 2 Views specification [DOM Level 2 Views]. Please, refer to additional information about conformance in the DOM Level 2 Core specification [DOM Level 2 Core].

Note: To create an instance of the UIEventinterface, use the feature string "UIEvents" as the value of the input parameter used with the createEvent method of the DocumentEventinterface.

Interface UIEvent (introduced in DOM Level 2)

The UIEvent interface provides specific contextual information associated with User Interface events.

IDL Definition

// Introduced in DOM Level 2: interface UIEvent : Event { readonly attribute views::AbstractView view; readonly attribute long detail; void initUIEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in views::AbstractView viewArg, in long detailArg); };

Attributes

detail of typelong, readonly

Specifies some detail information about the Event, depending on the type of event.

view of typeviews::AbstractView, readonly

The view attribute identifies theAbstractView from which the event was generated.

Methods

initUIEvent

The initUIEvent method is used to initialize the value of a UIEvent created through theDocumentEventinterface. This method may only be called before theUIEvent has been dispatched via thedispatchEvent method, though it may be called multiple times during that phase if necessary. If called multiple times, the final invocation takes precedence.

Parameters

typeArg of typeDOMString

Specifies the event type.

canBubbleArg of typeboolean

Specifies whether or not the event can bubble.

cancelableArg of typeboolean

Specifies whether or not the event's default action can be prevented.

viewArg of typeviews::AbstractView

Specifies the Event'sAbstractView.

detailArg of typelong

Specifies the Event's detail.

No Return Value

No Exceptions

The different types of such events that can occur are:

DOMFocusIn

The DOMFocusIn event occurs when an EventTargetreceives focus, for instance via a pointing device being moved onto an element or by tabbing navigation to the element. Unlike the HTML event focus, DOMFocusIn can be applied to any focusable EventTarget, not just FORM controls.

DOMFocusOut

The DOMFocusOut event occurs when a EventTargetloses focus, for instance via a pointing device being moved out of an element or by tabbing navigation out of the element. Unlike the HTML event blur, DOMFocusOut can be applied to any focusable EventTarget, not just FORM controls.

DOMActivate

The activate event occurs when an element is activated, for instance, thru a mouse click or a keypress. A numerical argument is provided to give an indication of the type of activation that occurs: 1 for a simple activation (e.g. a simple click or Enter), 2 for hyperactivation (for instance a double click or Shift Enter).

1.6.2. Mouse event types

The Mouse event module is composed of events listed in HTML 4.0 and additional events which are supported in DOM Level 0browsers. This event module is specifically designed for use with mouse input devices.

A DOM application may use the hasFeature(feature, version) method of the DOMImplementationinterface with parameter values "MouseEvents" and "2.0" (respectively) to determine whether or not the Mouse event module is supported by the implementation. In order to fully support this module, an implementation must also support the "UIEvents" feature defined in this specification. Please, refer to additional information about conformance in the DOM Level 2 Core specification [DOM Level 2 Core].

Note: To create an instance of the MouseEventinterface, use the feature string "MouseEvents" as the value of the input parameter used with the createEvent method of the DocumentEventinterface.

Interface MouseEvent (introduced in DOM Level 2)

The MouseEvent interface provides specific contextual information associated with Mouse events.

The detail attribute inherited from UIEventindicates the number of times a mouse button has been pressed and released over the same screen location during a user action. The attribute value is 1 when the user begins this action and increments by 1 for each full sequence of pressing and releasing. If the user moves the mouse between the mousedown and mouseup the value will be set to 0, indicating that no click is occurring.

In the case of nested elements mouse events are always targeted at the most deeply nested element. Ancestors of the targeted element may use bubbling to obtain notification of mouse events which occur within its descendent elements.

IDL Definition

// Introduced in DOM Level 2: interface MouseEvent : UIEvent { readonly attribute long screenX; readonly attribute long screenY; readonly attribute long clientX; readonly attribute long clientY; readonly attribute boolean ctrlKey; readonly attribute boolean shiftKey; readonly attribute boolean altKey; readonly attribute boolean metaKey; readonly attribute unsigned short button; readonly attribute EventTarget relatedTarget; void initMouseEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in views::AbstractView viewArg, in long detailArg, in long screenXArg, in long screenYArg, in long clientXArg, in long clientYArg, in boolean ctrlKeyArg, in boolean altKeyArg, in boolean shiftKeyArg, in boolean metaKeyArg, in unsigned short buttonArg, in EventTarget relatedTargetArg); };

Attributes

altKey of typeboolean, readonly

Used to indicate whether the 'alt' key was depressed during the firing of the event. On some platforms this key may map to an alternative key name.

button of typeunsigned short, readonly

During mouse events caused by the depression or release of a mouse button, button is used to indicate which mouse button changed state. The values for button range from zero to indicate the left button of the mouse, one to indicate the middle button if present, and two to indicate the right button. For mice configured for left handed use in which the button actions are reversed the values are instead read from right to left.

clientX of typelong, readonly

The horizontal coordinate at which the event occurred relative to the DOM implementation's client area.

clientY of typelong, readonly

The vertical coordinate at which the event occurred relative to the DOM implementation's client area.

ctrlKey of typeboolean, readonly

Used to indicate whether the 'ctrl' key was depressed during the firing of the event.

metaKey of typeboolean, readonly

Used to indicate whether the 'meta' key was depressed during the firing of the event. On some platforms this key may map to an alternative key name.

relatedTarget of type EventTarget, readonly

Used to identify a secondary EventTargetrelated to a UI event. Currently this attribute is used with the mouseover event to indicate the EventTargetwhich the pointing device exited and with the mouseout event to indicate the EventTargetwhich the pointing device entered.

screenX of typelong, readonly

The horizontal coordinate at which the event occurred relative to the origin of the screen coordinate system.

screenY of typelong, readonly

The vertical coordinate at which the event occurred relative to the origin of the screen coordinate system.

shiftKey of typeboolean, readonly

Used to indicate whether the 'shift' key was depressed during the firing of the event.

Methods

initMouseEvent

The initMouseEvent method is used to initialize the value of a MouseEvent created through the DocumentEventinterface. This method may only be called before theMouseEvent has been dispatched via thedispatchEvent method, though it may be called multiple times during that phase if necessary. If called multiple times, the final invocation takes precedence.

Parameters

typeArg of typeDOMString

Specifies the event type.

canBubbleArg of typeboolean

Specifies whether or not the event can bubble.

cancelableArg of typeboolean

Specifies whether or not the event's default action can be prevented.

viewArg of typeviews::AbstractView

Specifies the Event'sAbstractView.

detailArg of typelong

Specifies the Event's mouse click count.

screenXArg of typelong

Specifies the Event's screen x coordinate

screenYArg of typelong

Specifies the Event's screen y coordinate

clientXArg of typelong

Specifies the Event's client x coordinate

clientYArg of typelong

Specifies the Event's client y coordinate

ctrlKeyArg of typeboolean

Specifies whether or not control key was depressed during theEvent.

altKeyArg of typeboolean

Specifies whether or not alt key was depressed during the Event.

shiftKeyArg of typeboolean

Specifies whether or not shift key was depressed during the Event.

metaKeyArg of typeboolean

Specifies whether or not meta key was depressed during the Event.

buttonArg of typeunsigned short

Specifies the Event's mouse button.

relatedTargetArg of type EventTarget

Specifies the Event's related EventTarget.

No Return Value

No Exceptions

The different types of Mouse events that can occur are:

click

The click event occurs when the pointing device button is clicked over an element. A click is defined as a mousedown and mouseup over the same screen location. The sequence of these events is: If multiple clicks occur at the same screen location, the sequence repeats with the detail attribute incrementing with each repetition. This event is valid for most elements.

mousedown

The mousedown event occurs when the pointing device button is pressed over an element. This event is valid for most elements.

mouseup

The mouseup event occurs when the pointing device button is released over an element. This event is valid for most elements.

mouseover

The mouseover event occurs when the pointing device is moved onto an element. This event is valid for most elements.

mousemove

The mousemove event occurs when the pointing device is moved while it is over an element. This event is valid for most elements.

mouseout

The mouseout event occurs when the pointing device is moved away from an element. This event is valid for most elements..

1.6.3. Key events

The DOM Level 2 Event specification does not provide a key event module. An event module designed for use with keyboard input devices will be included in a later version of the DOM specification.

1.6.4. Mutation event types

The mutation event module is designed to allow notification of any changes to the structure of a document, including attr and text modifications. It may be noted that none of the mutation events listed are designated as cancelable. This stems from the fact that it is very difficult to make use of existing DOM interfaces which cause document modifications if any change to the document might or might not take place due to cancelation of the related event. Although this is still a desired capability, it was decided that it would be better left until the addition of transactions into the DOM.

Many single modifications of the tree can cause multiple mutation events to be fired. Rather than attempt to specify the ordering of mutation events due to every possible modification of the tree, the ordering of these events is left to the implementation.

A DOM application may use the hasFeature(feature, version) method of the DOMImplementationinterface with parameter values "MutationEvents" and "2.0" (respectively) to determine whether or not the Mutation event module is supported by the implementation. In order to fully support this module, an implementation must also support the "Events" feature defined in this specification. Please, refer to additional information about conformance in the DOM Level 2 Core specification [DOM Level 2 Core].

Note: To create an instance of the MutationEventinterface, use the feature string "MutationEvents" as the value of the input parameter used with the createEvent method of the DocumentEventinterface.

Interface MutationEvent (introduced in DOM Level 2)

The MutationEvent interface provides specific contextual information associated with Mutation events.

IDL Definition

// Introduced in DOM Level 2: interface MutationEvent : Event {

// attrChangeType const unsigned short MODIFICATION = 1; const unsigned short ADDITION = 2; const unsigned short REMOVAL = 3;

readonly attribute Node relatedNode; readonly attribute DOMString prevValue; readonly attribute DOMString newValue; readonly attribute DOMString attrName; readonly attribute unsigned short attrChange; void initMutationEvent(in DOMString typeArg, in boolean canBubbleArg, in boolean cancelableArg, in Node relatedNodeArg, in DOMString prevValueArg, in DOMString newValueArg, in DOMString attrNameArg, in unsigned short attrChangeArg); };

Definition group attrChangeType

An integer indicating in which way the Attr was changed.

Defined Constants

ADDITION

The Attr was just added.

MODIFICATION

The Attr was modified in place.

REMOVAL

The Attr was just removed.

Attributes

attrChange of type unsigned short, readonly

attrChange indicates the type of change which triggered the DOMAttrModified event. The values can beMODIFICATION, ADDITION, orREMOVAL.

attrName of typeDOMString, readonly

attrName indicates the name of the changedAttr node in a DOMAttrModified event.

newValue of typeDOMString, readonly

newValue indicates the new value of theAttr node in DOMAttrModified events, and of theCharacterData node in DOMCharDataModified events.

prevValue of typeDOMString, readonly

prevValue indicates the previous value of theAttr node in DOMAttrModified events, and of theCharacterData node in DOMCharDataModified events.

relatedNode of type Node, readonly

relatedNode is used to identify a secondary node related to a mutation event. For example, if a mutation event is dispatched to a node indicating that its parent has changed, therelatedNode is the changed parent. If an event is instead dispatched to a subtree indicating a node was changed within it, the relatedNode is the changed node. In the case of the DOMAttrModified event it indicates theAttr node which was modified, added, or removed.

Methods

initMutationEvent

The initMutationEvent method is used to initialize the value of a MutationEventcreated through the DocumentEventinterface. This method may only be called before theMutationEvent has been dispatched via thedispatchEvent method, though it may be called multiple times during that phase if necessary. If called multiple times, the final invocation takes precedence.

Parameters

typeArg of typeDOMString

Specifies the event type.

canBubbleArg of typeboolean

Specifies whether or not the event can bubble.

cancelableArg of typeboolean

Specifies whether or not the event's default action can be prevented.

relatedNodeArg of typeNode

Specifies the Event's related Node.

prevValueArg of typeDOMString

Specifies the Event'sprevValue attribute. This value may be null.

newValueArg of typeDOMString

Specifies the Event'snewValue attribute. This value may be null.

attrNameArg of typeDOMString

Specifies the Event'sattrName attribute. This value may be null.

attrChangeArg of typeunsigned short

Specifies the Event'sattrChange attribute

No Return Value

No Exceptions

The different types of Mutation events that can occur are:

DOMSubtreeModified

This is a general event for notification of all changes to the document. It can be used instead of the more specific events listed below. It may be fired after a single modification to the document or, at the implementation's discretion, after multiple changes have occurred. The latter use should generally be used to accomodate multiple changes which occur either simultaneously or in rapid succession. The target of this event is the lowest common parent of the changes which have taken place. This event is dispatched after any other events caused by the mutation have fired.

DOMNodeInserted

Fired when a node has been added as a child of another node. This event is dispatched after the insertion has taken place. The target of this event is the node being inserted.

DOMNodeRemoved

Fired when a node is being removed from its parent node. This event is dispatched before the node is removed from the tree. The target of this event is the node being removed.

DOMNodeRemovedFromDocument

Fired when a node is being removed from a document, either through direct removal of the Node or removal of a subtree in which it is contained. This event is dispatched before the removal takes place. The target of this event is the Node being removed. If the Node is being directly removed the DOMNodeRemoved event will fire before the DOMNodeRemovedFromDocument event.

DOMNodeInsertedIntoDocument

Fired when a node is being inserted into a document, either through direct insertion of the Node or insertion of a subtree in which it is contained. This event is dispatched after the insertion has taken place. The target of this event is the node being inserted. If the Node is being directly inserted the DOMNodeInserted event will fire before the DOMNodeInsertedIntoDocument event.

DOMAttrModified

Fired after an Attr has been modified on a node. The target of this event is the Node whoseAttr changed. The value of attrChange indicates whether the Attr was modified, added, or removed. The value of relatedNode indicates the Attr node whose value has been affected. It is expected that string based replacement of an Attr value will be viewed as a modification of the Attr since its identity does not change. Subsequently replacement of the Attr node with a different Attr node is viewed as the removal of the first Attr node and the addition of the second.

DOMCharacterDataModified

Fired after CharacterData within a node has been modified but the node itself has not been inserted or deleted. This event is also triggered by modifications to PI elements. The target of this event is the CharacterData node.

1.6.5. HTML event types

The HTML event module is composed of events listed in HTML 4.0 and additional events which are supported in DOM Level 0browsers.

A DOM application may use the hasFeature(feature, version) method of the DOMImplementationinterface with parameter values "HTMLEvents" and "2.0" (respectively) to determine whether or not the HTML event module is supported by the implementation. In order to fully support this module, an implementation must also support the "Events" feature defined in this specification. Please, refer to additional information about conformance in the DOM Level 2 Core specification [DOM Level 2 Core].

Note: To create an instance of the Event interface for the HTML event module, use the feature string "HTMLEvents" as the value of the input parameter used with thecreateEvent method of the DocumentEventinterface.

The HTML events use the base DOM Event interface to pass contextual information.

The different types of such events that can occur are:

load

The load event occurs when the DOM implementation finishes loading all content within a document, all frames within a FRAMESET, or an OBJECT element.

unload

The unload event occurs when the DOM implementation removes a document from a window or frame. This event is valid for BODY and FRAMESET elements.

abort

The abort event occurs when page loading is stopped before an image has been allowed to completely load. This event applies to OBJECT elements.

error

The error event occurs when an image does not load properly or when an error occurs during script execution. This event is valid for OBJECT elements, BODY elements, and FRAMESET element.

select

The select event occurs when a user selects some text in a text field. This event is valid for INPUT and TEXTAREA elements.

change

The change event occurs when a control loses the input focus and its value has been modified since gaining focus. This event is valid for INPUT, SELECT, and TEXTAREA. element.

submit

The submit event occurs when a form is submitted. This event only applies to the FORM element.

reset

The reset event occurs when a form is reset. This event only applies to the FORM element.

focus

The focus event occurs when an element receives focus either via a pointing device or by tabbing navigation. This event is valid for the following elements: LABEL, INPUT, SELECT, TEXTAREA, and BUTTON.

blur

The blur event occurs when an element loses focus either via the pointing device or by tabbing navigation. This event is valid for the following elements: LABEL, INPUT, SELECT, TEXTAREA, and BUTTON.

resize

The resize event occurs when a document view is resized.

scroll

The scroll event occurs when a document view is scrolled.