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111 lines
5.3 KiB
HTML
111 lines
5.3 KiB
HTML
<article id="wikiArticle">
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<div>
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</div>
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<h2 id="Summary" name="Summary">概述</h2>
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<p><code><strong>Math.sqrt()</strong></code> 函数返回一个数的平方根，即：</p>
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<p><math display="block"><semantics><mrow><mo>∀</mo><mi>x</mi><mo>≥</mo><mn>0</mn><mo>,</mo><mstyle mathvariant="monospace"><mrow><mi>M</mi><mi>a</mi><mi>t</mi><mi>h</mi><mo>.</mo><mi>s</mi><mi>q</mi><mi>r</mi><mi>t</mi><mo stretchy="false">(</mo><mi>x</mi><mo stretchy="false">)</mo></mrow></mstyle><mo>=</mo><msqrt><mi>x</mi></msqrt><mo>=</mo><mtext>the unique</mtext><mspace width="thickmathspace"></mspace><mi>y</mi><mo>≥</mo><mn>0</mn><mspace width="thickmathspace"></mspace><mtext>such that</mtext><mspace width="thickmathspace"></mspace><msup><mi>y</mi><mn>2</mn></msup><mo>=</mo><mi>x</mi></mrow><annotation encoding="TeX">\forall x \geq 0, \mathtt{Math.sqrt(x)} = \sqrt{x} = \text{the unique} \; y \geq 0 \; \text{such that} \; y^2 = x</annotation></semantics></math></p>
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<h2 id="Syntax" name="Syntax">语法</h2>
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<pre><code class="language-javascript"><code>Math.sqrt(<em>x</em>) </code></code></pre>
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<h3 id="Parameters" name="Parameters">参数</h3>
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<dl>
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<dt>
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<code>x</code></dt>
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<dd>
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一个数值</dd>
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</dl>
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<h2 id="Description" name="Description">描述</h2>
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<p>如果参数 <code>number</code> 为负值，则 <code>sqrt</code> 返回 <code>NaN</code>。</p>
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<p>由于 <code>sqrt</code> 是 <code>Math</code> 的静态方法，所以应该像这样使用：<code>Math.sqrt()</code>，而不是作为你创建的 <code>Math</code> 实例的方法。</p>
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<h2 id="Examples" name="Examples">示例</h2>
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<h3 id="Example:_Using_Math.sqrt" name="Example:_Using_Math.sqrt">例子：使用 <code>Math.sqrt</code></h3>
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<pre><code class="language-js">Math.sqrt(9); // 3
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Math.sqrt(2); // 1.414213562373095
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Math.sqrt(1); // 1
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Math.sqrt(0); // 0
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Math.sqrt(-1); // NaN</code></pre>
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<h2 id="规范">规范</h2>
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<table class="standard-table">
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<tbody>
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<tr>
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<th scope="col">规范版本</th>
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<th scope="col">规范状态</th>
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<th scope="col">注解</th>
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</tr>
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<tr>
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<td>ECMAScript 1st Edition. Implemented in JavaScript 1.0</td>
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<td>Standard</td>
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<td>Initial definition.</td>
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</tr>
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<tr>
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<td><a class="external" href="https://www.ecma-international.org/ecma-262/5.1/#sec-15.8.2.17" hreflang="en" lang="en" rel="noopener">ECMAScript 5.1 (ECMA-262)<br/><small lang="zh-CN">Math.sqrt</small></a></td>
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<td><span class="spec-Standard">Standard</span></td>
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<td> </td>
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</tr>
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<tr>
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<td><a class="external" href="https://www.ecma-international.org/ecma-262/6.0/#sec-math.sqrt" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">Math.sqrt</small></a></td>
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<td><span class="spec-Standard">Standard</span></td>
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<td> </td>
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</tr>
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</tbody>
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</table>
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<h2 id="浏览器兼容性">浏览器兼容性</h2>
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<p></p><div class="blockIndicator warning"><strong><a class="external" href="https://github.com/mdn/browser-compat-data" rel="noopener">We're converting our compatibility data into a machine-readable JSON format</a></strong>.
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This compatibility table still uses the old format,
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because we haven't yet converted the data it contains.
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<strong><a class="new" href="/zh-CN/docs/MDN/Contribute/Structures/Compatibility_tables" rel="nofollow">Find out how you can help!</a></strong></div>
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<div class="htab">
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<a id="AutoCompatibilityTable" name="AutoCompatibilityTable"></a>
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<ul>
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<li class="selected"><a>Desktop</a></li>
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<li><a>Mobile</a></li>
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</ul>
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</div><p></p>
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<div id="compat-desktop">
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<table class="compat-table">
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<tbody>
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<tr>
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<th>Feature</th>
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<th>Chrome</th>
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<th>Firefox (Gecko)</th>
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<th>Internet Explorer</th>
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<th>Opera</th>
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<th>Safari</th>
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</tr>
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<tr>
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<td>Basic support</td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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</tr>
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</tbody>
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</table>
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</div>
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<div id="compat-mobile">
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<table class="compat-table">
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<tbody>
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<tr>
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<th>Feature</th>
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<th>Android</th>
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<th>Chrome for Android</th>
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<th>Firefox Mobile (Gecko)</th>
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<th>IE Mobile</th>
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<th>Opera Mobile</th>
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<th>Safari Mobile</th>
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</tr>
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<tr>
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<td>Basic support</td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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<td><span style="color: #888;" title="Please update this with the earliest version of support.">(Yes)</span></td>
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</tr>
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</tbody>
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</table>
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</div>
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<p> </p>
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</article> |