---
title: EventTarget
slug: Web/API/EventTarget
tags:
  - API
  - DOM
  - DOM Events
  - Interface
  - NeedsTranslation
  - TopicStub
  - 待翻譯
translation_of: Web/API/EventTarget
---
<p>{{ ApiRef("DOM Events") }}</p>

<p><strong><code>EventTarget</code></strong> 介面定義了其實作的物件具有接收事件的能力，也可能擁有處理事件的監聽器。</p>

<p>除了最為常見的 {{domxref("Element")}}、{{domxref("Document")}} 與 {{domxref("Window")}} 繼承或實作了 <code>EventTarget</code> 介面之外，其它的物件還有 {{domxref("XMLHttpRequest")}}、{{domxref("AudioNode")}}、{{domxref("AudioContext")}}⋯等等。</p>

<p>許多 <code>EventTarget</code>（包括 Element、Document 和 Window）除了透過 {{domxref("EventTarget.addEventListener()", "addEventListener()")}} 方法外，還可藉由 {{domxref("Document_Object_Model", "DOM")}} 物件的屬性（{{Glossary("property/JavaScript", "property")}}）或 <a href="/zh-TW/docs/Web/HTML/Element">HTML 元素</a>屬性（{{Glossary("attribute")}}）來設定<a href="/zh-TW/docs/Web/Guide/DOM/Events/Event_handlers">事件處理器</a>。</p>

<p>{{InheritanceDiagram}}</p>

<h2 id="方法" name="方法">方法</h2>

<dl>
 <dt>{{domxref("EventTarget.addEventListener()")}}</dt>
 <dd>於 <code>EventTarget</code> 物件上註冊指定事件的監聽器。</dd>
 <dt>{{domxref("EventTarget.removeEventListener()")}}</dt>
 <dd>移除 <code>EventTarget</code> 物件上的指定事件監聽器。</dd>
 <dt>{{domxref("EventTarget.dispatchEvent()")}}</dt>
 <dd>對此 <code>EventTarget</code> 物件派送（dispatch）一個事件物件，也就是於此 <code>EventTarget</code> 物件上觸發一個指定的事件物件實體。</dd>
</dl>

<h3 id="Mozilla_chrome_code_的額外方法">Mozilla chrome code 的額外方法</h3>

<p>Mozilla extensions for use by JS-implemented event targets to implement on* properties. See also <a href="/docs/Mozilla/WebIDL_bindings">WebIDL bindings</a>.</p>

<ul>
 <li>void <strong>setEventHandler</strong>(DOMString type, EventHandler handler) {{non-standard_inline}}</li>
 <li>EventHandler <strong>getEventHandler</strong>(DOMString type) {{non-standard_inline}}</li>
</ul>

<h2 id="範例">範例</h2>

<h3 id="_Simple_implementation_of_EventTarget" name="_Simple_implementation_of_EventTarget">Simple implementation of EventTarget</h3>

<pre class="brush: js">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 &lt; 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];
  event.target = this;
  for (var i = 0, l = stack.length; i &lt; l; i++) {
    stack[i].call(this, event);
  }
  return !event.defaultPrevented;
};
</pre>

<p>{{ EmbedLiveSample('_Simple_implementation_of_EventTarget') }}</p>

<h2 id="Specification" name="Specification">規範</h2>

<table class="standard-table">
 <tbody>
  <tr>
   <th scope="col">Specification</th>
   <th scope="col">Status</th>
   <th scope="col">Comment</th>
  </tr>
  <tr>
   <td>{{SpecName('DOM WHATWG', '#interface-eventtarget', 'EventTarget')}}</td>
   <td>{{Spec2('DOM WHATWG')}}</td>
   <td>No change.</td>
  </tr>
  <tr>
   <td>{{SpecName('DOM3 Events', 'DOM3-Events.html#interface-EventTarget', 'EventTarget')}}</td>
   <td>{{Spec2('DOM3 Events')}}</td>
   <td>A few parameters are now optional (<code>listener</code>), or accepts the <code>null</code> value (<code>useCapture</code>).</td>
  </tr>
  <tr>
   <td>{{SpecName('DOM2 Events', 'events.html#Events-EventTarget', 'EventTarget')}}</td>
   <td>{{Spec2('DOM2 Events')}}</td>
   <td>Initial definition.</td>
  </tr>
 </tbody>
</table>

<h2 id="Browser_Compatibility" name="Browser_Compatibility">瀏覽器相容性</h2>

{{Compat("api.EventTarget")}}

<h2 id="參見">參見</h2>

<ul>
 <li><a href="/docs/Web/Reference/Events">Event reference</a> - the events available in the platform.</li>
 <li><a href="/docs/Web/Guide/DOM/Events">Event developer guide</a></li>
 <li>{{domxref("Event")}} interface</li>
</ul>