---
title: WebGL2RenderingContext.beginQuery()
slug: Web/API/WebGL2RenderingContext/beginQuery
translation_of: Web/API/WebGL2RenderingContext/beginQuery
---
<div>{{APIRef("WebGL")}} {{SeeCompatTable}}</div>

<p><a href="/en-US/docs/Web/API/WebGL_API">WebGL 2 API</a> 的<strong><code>WebGL2RenderingContext.beginQuery()</code></strong> 方法启动一个异步查询，<code>target</code> 参数表明是哪种类型的查询。</p>

<h2 id="语法">语法</h2>

<pre class="syntaxbox">void <var>gl</var>.beginQuery(<var>target</var>, <var>query</var>);
</pre>

<h3 id="参数">参数</h3>

<dl>
 <dt>target</dt>
 <dd> {{domxref("GLenum")}} 指定查询个的target， 可能的值有:
 <ul>
  <li><code>gl.ANY_SAMPLES_PASSED</code>: Specifies an occlusion query: these queries detect whether an object is visible (whether the scoped drawing commands pass the depth test and if so, how many samples pass).</li>
  <li><code>gl.ANY_SAMPLES_PASSED_CONSERVATIVE</code>: 和以上一样， 但是是一个不精确和更快的版本。</li>
  <li><code>gl.TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN</code>: Number of primitives that are written to transform feedback buffers.</li>
 </ul>
 </dd>
 <dt><code>query</code></dt>
 <dd>一个{{domxref("WebGLQuery")}} 对象用于查询。</dd>
</dl>

<h3 id="返回值">返回值</h3>

<p>None.</p>

<h2 id="例子">例子</h2>

<pre class="brush: js">var query = gl.createQuery();
gl.beginQuery(gl.ANY_SAMPLES_PASSED, query);

// ...
</pre>

<h2 id="规范">规范</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('WebGL2', "#3.7.12", "beginQuery")}}</td>
   <td>{{Spec2('WebGL2')}}</td>
   <td>Initial definition.</td>
  </tr>
  <tr>
   <td>{{SpecName('OpenGL ES 3.0', "glBeginQuery.xhtml", "glBeginQuery")}}</td>
   <td>{{Spec2('OpenGL ES 3.0')}}</td>
   <td>Man page of the (similar) OpenGL API.</td>
  </tr>
 </tbody>
</table>

<h2 id="浏览器兼容">浏览器兼容</h2>

<p>{{Compat("api.WebGL2RenderingContext.beginQuery")}}</p>

<h2 id="参考">参考</h2>

<ul>
 <li>{{domxref("WebGLQuery")}}</li>
</ul>