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  3. nsIDOMEventTarget
Table of contents
  1. 1. Method overview
  2. 2. Methods
    1. 2.1. addEventListener()
          1. 2.1.1.1.1. Parameters
    2. 2.2. removeEventListener()
          1. 2.2.1.1.1. Parameters
    3. 2.3. dispatchEvent()
          1. 2.3.1.1.1. Parameters
          2. 2.3.1.1.2. Return value
          3. 2.3.1.1.3. Throws

nsIDOMEventTarget

Table of contents
  1. 1. Method overview
  2. 2. Methods
    1. 2.1. addEventListener()
          1. 2.1.1.1.1. Parameters
    2. 2.2. removeEventListener()
          1. 2.2.1.1.1. Parameters
    3. 2.3. dispatchEvent()
          1. 2.3.1.1.1. Parameters
          2. 2.3.1.1.2. Return value
          3. 2.3.1.1.3. Throws

The nsIDOMEventTarget interface is the interface implemented by all event targets in the Document Object Model.


nsIDOMEventTarget is defined in dom/public/idl/events/nsIDOMEventTarget.idl . It is scriptable and has been frozen since Mozilla 1.8 .

Inherits from: nsISupports

Method overview

void addEventListener(in DOMString type, in nsIDOMEventListener listener, in boolean useCapture);
void removeEventListener(in DOMString type, in nsIDOMEventListener listener, in boolean useCapture);
void dispatchEvent(in nsIDOMEvent evt)raises(DOMException));

Methods

addEventListener()

This method allows the registration of event listeners on the event target. If an EventListener is 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 EventListener to be called twice and since they are discarded they do not need to be removed with the removeEventListener method. 

  void addEventListener(
     in DOMString type,
     in nsIDOMEventListener listener,
     in boolean useCapture
  );
Parameters
type
The event type for which the user is registering.
listener
The listener parameter takes an interface implemented by the user which contains the methods to be called when the event occurs.
useCapture
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 EventListener before being dispatched to any EventTargets beneath them in the tree. Events which are bubbling upward through the tree will not trigger an EventListener designated to use capture.

removeEventListener()

This method allows the removal of event listeners from the event target. If an EventListener is 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 EventListener on the EventTarget has no effect. 

  void removeEventListener(
     in DOMString type,
     in nsIDOMEventListener listener,
     in boolean useCapture
  );
Parameters
type
Specifies the event type of the EventListener being removed.
listener
The EventListener parameter indicates the EventListener to be removed.
useCapture
Specifies whether the EventListener being 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.

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 dispatchEvent is called. 

  boolean dispatchEvent(
     in nsIDOMEvent evt)raises(DOMException
  );
Parameters
evt
Specifies the event type, behavior, and contextual information to be used in processing the event.
Return value

Indicates whether any of the listeners which handled the event called preventDefault. If preventDefault was called the value is false, else the value is true.

Throws

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

Page last modified 18:18, 28 Dec 2007 by Kglee?

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