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---
title: compositionstart
slug: Web/API/Element/compositionstart_event
tags:
- Element
- Event
- Input method
- compositionstart
- 事件
- 参考
translation_of: Web/API/Element/compositionstart_event
original_slug: Web/Events/compositionstart
---
<p>文本合成系统如 {{glossary("input method editor")}}（即输入法编辑器）开始新的输入合成时会触发 <strong><code>compositionstart</code></strong> 事件。</p>
<p>例如，当用户使用拼音输入法开始输入汉字时，这个事件就会被触发。</p>
<table class="properties">
<tbody>
<tr>
<td><strong>Bubbles</strong></td>
<td>Yes</td>
</tr>
<tr>
<td><strong>Cancelable</strong></td>
<td>Yes</td>
</tr>
<tr>
<td><strong>Interface</strong></td>
<td>{{domxref("CompositionEvent")}}</td>
</tr>
<tr>
<td><strong>Event handler property</strong></td>
<td>
<table>
<tbody>
<tr>
<td>None</td>
</tr>
</tbody>
</table>
</td>
</tr>
</tbody>
</table>
<h2 id="示例">示例</h2>
<pre>const inputElement = document.querySelector('input[type="text"]');
inputElement.addEventListener('compositionstart', (event) => {
console.log(`generated characters were: ${event.data}`);
});</pre>
<h3 id="动态演示">动态演示</h3>
<h4 id="HTML">HTML</h4>
<pre><div class="control">
<label for="name">On macOS, click in the textbox below,<br> then type <kbd>option</kbd> + <kbd>`</kbd>, then <kbd>a</kbd>:</label>
<input type="text" id="example" name="example">
</div>
<div class="event-log">
<label>Event log:</label>
<textarea readonly class="event-log-contents" rows="8" cols="25"></textarea>
<button class="clear-log">Clear</button>
</div></pre>
<h4 id="CSS">CSS</h4>
<pre>body {
padding: .2rem;
display: grid;
grid-template-areas: "control log";
}
.control {
grid-area: control;
}
.event-log {
grid-area: log;
}
.event-log-contents {
resize: none;
}
label, button {
display: block;
}
input[type="text"] {
margin: .5rem 0;
}
kbd {
border-radius: 3px;
padding: 1px 2px 0;
border: 1px solid black;
}
</pre>
<h4 id="JS">JS</h4>
<pre>const inputElement = document.querySelector('input[type="text"]');
const log = document.querySelector('.event-log-contents');
const clearLog = document.querySelector('.clear-log');
clearLog.addEventListener('click', () => {
log.textContent = '';
});
function handleEvent(event) {
log.textContent = log.textContent + `${event.type}: ${event.data}\n`;
}
inputElement.addEventListener('compositionstart', handleEvent);
inputElement.addEventListener('compositionupdate', handleEvent);
inputElement.addEventListener('compositionend', handleEvent);
</pre>
<h4 id="结果">结果</h4>
<p><iframe class="live-sample-frame sample-code-frame" frameborder="0" height="180px" id="frame_Live_example" src="https://mdn.mozillademos.org/en-US/docs/Web/API/Element/compositionstart_event$samples/Live_example?revision=1606277" width="100%"></iframe></p>
<h2 id="规范">规范</h2>
<table>
<thead>
<tr>
<th scope="col">规范</th>
<th scope="col">状态</th>
</tr>
</thead>
<tbody>
<tr>
<td>{{SpecName('UI Events', '#event-type-compositionstart')}}</td>
<td>{{Spec2('UI Events')}}</td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<p>{{Compat("api.Element.compositionstart_event")}}</p>
<h2 id="参见">参见</h2>
<ul>
<li>相关事件：{{domxref("Element/compositionend_event", "compositionend")}}, {{domxref("Element/compositionupdate_event", "compositionupdate")}}.</li>
</ul>
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