--- 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 < 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 < 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>