EventTarget

EventTarget is a DOM 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 onevent properties and attributes.

Constructor

EventTarget(): Creates a new EventTarget object instance.

Methods

EventTarget.addEventListener(): Registers an event handler of a specific event type on the EventTarget.
EventTarget.removeEventListener(): Removes an event listener from the EventTarget.
EventTarget.dispatchEvent(): Dispatches an event to this EventTarget.

Example

Simple implementation of EventTarget

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;
    }
  }
};

EventTarget.prototype.dispatchEvent = function(event) {
  if (!(event.type in this.listeners)) {
    return true;
  }
  var stack = this.listeners[event.type].slice();

  for (var i = 0, l = stack.length; i < l; i++) {
    stack[i].call(this, event);
  }
  return !event.defaultPrevented;
};

Specifications

Specification
DOM Standard (DOM) # interface-eventtarget

Browser compatibility

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet
`EventTarget`	1	12	1	6	7	1 `window.EventTarget` did not exist on versions of Safari before 10.1.	1	18	4	10.1	1 `window.EventTarget` did not exist on versions of Safari iOS before 10.3.	1.0
`EventTarget`	64	79	59	No	51	14	64	64	59	47	14	9.0
`addEventListener`	1 Before Chrome 49, the `type` and `listener` parameters were optional.	12	1	9 6-11 Older versions of IE supported an equivalent, proprietary `EventTarget.attachEvent()` method.	7	1	1 Before Chrome 49, the `type` and `listener` parameters were optional.	18 Before Chrome 49, the `type` and `listener` parameters were optional.	4	10.1	1	1.0 Before Samsung Internet 5.0, the `type` and `listener` parameters were optional.
`dispatchEvent`	4	12	2	9 6-11 Older versions of IE supported an equivalent, proprietary `EventTarget.fireEvent()` method.	9	3.1	4	18	4	10.1	3	1.0
`removeEventListener`	1	12	1	9 6-11 Older versions of IE supported an equivalent, proprietary `EventTarget.detachEvent()` method.	7	1	1	18	4	10.1	1	1.0