EventTarget
EventTarget
is an interface implemented by objects that can receive events and may have listeners for them.
Element
, document
, and window
are the most common event targets, but other objects can be event targets too, for example XMLHttpRequest
, AudioNode
, AudioContext
, and others.
Many event targets (including elements, documents, and windows) also support setting event handlers via on...
properties and attributes.
Methods
EventTarget.addEventListener()
- Register an event handler of a specific event type on the
EventTarget
. EventTarget.removeEventListener()
- Removes an event listener from the
EventTarget
. EventTarget.dispatchEvent()
- Dispatch an event to this
EventTarget
.
Additional methods for Mozilla chrome code
Mozilla extensions for use by JS-implemented event targets to implement on* properties. See also WebIDL bindings.
- void setEventHandler(DOMString type, EventHandler handler)
- EventHandler getEventHandler(DOMString type)
Example:
Simple implementation of EventTarget
JavaScript
Copy Code
var EventTarget = function() { this.listeners = {}; }; EventTarget.prototype.listeners = null; EventTarget.prototype.addEventListener = function(type, callback) { if(!(type in this.listeners)) { this.listeners[type] = []; } this.listeners[type].push(callback); }; EventTarget.prototype.removeEventListener = function(type, callback) { if(!(type in this.listeners)) { return; } var stack = this.listeners[type]; for(var i = 0, l = stack.length; i < l; i++) { if(stack[i] === callback){ stack.splice(i, 1); return this.removeEventListener(type, callback); } } }; EventTarget.prototype.dispatchEvent = function(event) { if(!(event.type in this.listeners)) { return; } var stack = this.listeners[event.type]; event.target = this; for(var i = 0, l = stack.length; i < l; i++) { stack[i].call(this, event); } };
Specifications
Specification | Status | Comment |
---|---|---|
DOM The definition of 'EventTarget' in that specification. |
Living Standard | No change. |
Document Object Model (DOM) Level 3 Events Specification The definition of 'EventTarget' in that specification. |
Working Draft | A few parameters are now optional (listener ), or accepts the null value (useCapture ). |
Document Object Model (DOM) Level 2 Events Specification The definition of 'EventTarget' in that specification. |
Recommendation | Initial definition. |
Browser compatibility
Feature | Chrome | Firefox (Gecko) | Internet Explorer | Opera | Safari (WebKit) |
---|---|---|---|---|---|
Basic support | 1.0 | 1.0 (1.7 or earlier) | 9.0 | 7 | 1.0[1] |
Feature | Android | Firefox Mobile (Gecko) | IE Mobile | Opera Mobile | Safari Mobile |
---|---|---|---|---|---|
Basic support | 1.0 | 1.0 (1) | 9.0 | 6.0 | 1.0 |
[1] window.EventTarget
does not exist.
See Also
- Event reference - the events available in the platform.
- Event developer guide
Event
interface
License
© 2016 Mozilla Contributors
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-us/docs/web/api/eventtarget