uTools-Manuals/docs/javascript/Reference/Statements/do...while.html

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<p><strong><code>do...while</code> 语句</strong><span lang="zh-CN"><span>创建一个执行指定语句的循环，直到</span></span><code>condition</code><span lang="zh-CN"><span>值为 false。</span><span>在执行</span></span><code>statement</code> <span lang="zh-CN"><span>后检测</span></span><code>condition</code><span lang="zh-CN"><span>，所以指定的</span></span><code>statement</code><span lang="zh-CN"><span>至少执行一次。</span></span></p>
<h2 id="Syntax" name="Syntax">语法</h2>
<pre><code class="language-javascript">do
   <em>statement</em>
while (<em>condition</em>);
</code></pre>
<dl>
<dt><code>statement</code></dt>
<dd><span class="short_text" id="result_box" lang="zh-CN"><span>执行至少一次的语句，并在每次 </span></span><code>condition</code> <span class="short_text" lang="zh-CN"><span>值为真时重新执行。</span></span>想执行多行语句，可使用<span style="line-height: 19.0909080505371px;"><a href="Reference/Statements/block" title="块语句（或其他语言的复合语句）用于组合零个或多个语句。该块由一对大括号界定，可以是labelled："><code>block</code></a></span>语句<span style="line-height: 19.0909080505371px;">（</span><code style="font-style: normal; line-height: 19.0909080505371px;">{ ... }</code><span style="line-height: 19.0909080505371px;">）</span>包裹这些语句。</dd>
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<dt><code>condition</code></dt>
<dd>循环中每次都会计算的表达式。如果 <code>condition</code> 值为真， <code>statement</code> 会再次执行。当 <code>condition</code> <span style="line-height: 19.0909080505371px;">值为假</span>，则跳到<code>do...while</code>之后的语句。</dd>
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<h2 id="Examples" name="Examples">示例</h2>
<h3 id="Example:_Using_do...while" name="Example:_Using_do...while">使用 <code>do...while</code></h3>
<p>下面的例子中，<code>do...while</code> 循环至少迭代一次，并且继续迭代直到 <code>i</code>不再小于 5 时结束。</p>
<h3 id="HTML_内容">HTML 内容</h3>
<pre><code class="language-html line-numbers language-html"><code class="language-html"><span class="tag token"><span class="tag token"><span class="punctuation token">&lt;</span>div</span> <span class="attr-name token">id</span><span class="attr-value token"><span class="punctuation token">=</span><span class="punctuation token">"</span>example<span class="punctuation token">"</span></span><span class="punctuation token">&gt;</span></span><span class="tag token"><span class="tag token"><span class="punctuation token">&lt;/</span>div</span><span class="punctuation token">&gt;</span></span></code></code></pre>
<h3 id="JavaScript_内容">JavaScript 内容</h3>
<pre><code  class="language-javascript"><code class="language-js"><span class="keyword token">var</span> result <span class="operator token">=</span> <span class="string token">''</span><span class="punctuation token">;</span>
<span class="keyword token">var</span> i <span class="operator token">=</span> <span class="number token">0</span><span class="punctuation token">;</span>
<span class="keyword token">do</span> <span class="punctuation token">{</span>
   i <span class="operator token">+</span><span class="operator token">=</span> <span class="number token">1</span><span class="punctuation token">;</span>
   result <span class="operator token">+</span><span class="operator token">=</span> i <span class="operator token">+</span> <span class="string token">' '</span><span class="punctuation token">;</span>
<span class="punctuation token">}</span> <span class="keyword token">while</span> <span class="punctuation token">(</span>i <span class="operator token">&lt;</span> <span class="number token">5</span><span class="punctuation token">)</span><span class="punctuation token">;</span>
document<span class="punctuation token">.</span><span class="function token">getElementById</span><span class="punctuation token">(</span><span class="string token">'example'</span><span class="punctuation token">)</span><span class="punctuation token">.</span>innerHTML <span class="operator token">=</span> result<span class="punctuation token">;</span></code></code></pre>
<h3 id="结果">结果</h3>
<p><iframe class="live-sample-frame sample-code-frame" frameborder="0" id="frame_Examples" src="https://mdn.mozillademos.orgReference/Statements/do...while$samples/Examples?revision=1504957"></iframe></p>
<h2 id="规范">规范</h2>
<table class="standard-table">
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<th scope="col">Specification</th>
<th scope="col">Status</th>
<th scope="col">Comment</th>
</tr>
<tr>
<td><a class="external" href="https://www.ecma-international.org/publications/files/ECMA-ST-ARCH/ECMA-262,%203rd%20edition,%20December%201999.pdf" hreflang="en" lang="en" rel="noopener" title="ECMAScript 3rd Edition (ECMA-262)">ECMAScript 3rd Edition (ECMA-262)</a></td>
<td><span class="spec-Standard">Standard</span></td>
<td>Initial definition. Implemented in JavaScript 1.2</td>
</tr>
<tr>
<td><a class="external" href="https://www.ecma-international.org/ecma-262/5.1/#sec-12.6.1" hreflang="en" lang="en" rel="noopener">ECMAScript 5.1 (ECMA-262)<br/><small lang="zh-CN">do-while statement</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td> </td>
</tr>
<tr>
<td><a class="external" href="https://www.ecma-international.org/ecma-262/6.0/#sec-do-while-statement" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">do-while statement</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td>Trailing ; is now optional.</td>
</tr>
<tr>
<td><a class="external" href="https://tc39.github.io/ecma262/#sec-do-while-statement" hreflang="en" lang="en" rel="noopener">ECMAScript Latest Draft (ECMA-262)<br/><small lang="zh-CN">do-while statement</small></a></td>
<td><span class="spec-Draft">Draft</span></td>
<td> </td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容">浏览器兼容</h2>
<div class="hidden">The compatibility table on this page is generated from structured data. If you'd like to contribute to the data, please check out <a class="external" href="https://github.com/mdn/browser-compat-data" rel="noopener">https://github.com/mdn/browser-compat-data</a> and send us a pull request.</div>
<p></p><div class="bc-data"><a class="bc-github-link external" href="https://github.com/mdn/browser-compat-data" rel="noopener">Update compatibility data on GitHub</a><table class="bc-table bc-table-js"><thead><tr class="bc-platforms"><td></td><th class="bc-platform-desktop" colspan="6"><span>Desktop</span></th><th class="bc-platform-mobile" colspan="7"><span>Mobile</span></th><th class="bc-platform-server" colspan="1"><span>Server</span></th></tr><tr class="bc-browsers"><td></td><th class="bc-browser-chrome"><span class="bc-head-txt-label bc-head-icon-chrome">Chrome</span></th><th class="bc-browser-edge"><span class="bc-head-txt-label bc-head-icon-edge">Edge</span></th><th class="bc-browser-firefox"><span class="bc-head-txt-label bc-head-icon-firefox">Firefox</span></th><th class="bc-browser-ie"><span class="bc-head-txt-label bc-head-icon-ie">Internet Explorer</span></th><th class="bc-browser-opera"><span class="bc-head-txt-label bc-head-icon-opera">Opera</span></th><th class="bc-browser-safari"><span class="bc-head-txt-label bc-head-icon-safari">Safari</span></th><th class="bc-browser-webview_android"><span class="bc-head-txt-label bc-head-icon-webview_android">Android webview</span></th><th class="bc-browser-chrome_android"><span class="bc-head-txt-label bc-head-icon-chrome_android">Chrome for Android</span></th><th class="bc-browser-edge_mobile"><span class="bc-head-txt-label bc-head-icon-edge_mobile">Edge Mobile</span></th><th class="bc-browser-firefox_android"><span class="bc-head-txt-label bc-head-icon-firefox_android">Firefox for Android</span></th><th class="bc-browser-opera_android"><span class="bc-head-txt-label bc-head-icon-opera_android">Opera for Android</span></th><th class="bc-browser-safari_ios"><span class="bc-head-txt-label bc-head-icon-safari_ios">Safari on iOS</span></th><th class="bc-browser-samsunginternet_android"><span class="bc-head-txt-label bc-head-icon-samsunginternet_android">Samsung Internet</span></th><th class="bc-browser-nodejs"><span class="bc-head-txt-label bc-head-icon-nodejs">Node.js</span></th></tr></thead><tbody><tr><th scope="row"><code>do...while</code></th><td class="bc-supports-yes bc-browser-chrome"><span class="bc-browser-name">Chrome</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-edge"><span class="bc-browser-name">Edge</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-firefox"><span class="bc-browser-name">Firefox</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              1</td><td class="bc-supports-yes bc-browser-ie"><span class="bc-browser-name">IE</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              6</td><td class="bc-supports-yes bc-browser-opera"><span class="bc-browser-name">Opera</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-safari"><span class="bc-browser-name">Safari</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-webview_android"><span class="bc-browser-name">WebView Android</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-chrome_android"><span class="bc-browser-name">Chrome Android</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-edge_mobile"><span class="bc-browser-name">Edge Mobile</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-firefox_android"><span class="bc-browser-name">Firefox Android</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              4</td><td class="bc-supports-yes bc-browser-opera_android"><span class="bc-browser-name">Opera Android</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-safari_ios"><span class="bc-browser-name">Safari iOS</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-samsunginternet_android"><span class="bc-browser-name">Samsung Internet Android</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td><td class="bc-supports-yes bc-browser-nodejs"><span class="bc-browser-name">nodejs</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              Yes</td></tr></tbody></table><section class="bc-legend" id="sect1"><h3 class="offscreen" id="Legend">Legend</h3><dl><dt><span class="bc-supports-yes bc-supports">
<abbr class="bc-level bc-level-yes only-icon" title="Full support">
<span>Full support</span>
                  
                </abbr></span></dt><dd>Full support</dd></dl></section></div><p></p>
<h2 id="See_also" name="See_also">相关链接</h2>
<ul>
<li><a href="Reference/Statements/while" title="while 语句可以在某个条件表达式为真的前提下，循环执行指定的一段代码，直到那个表达式不为真时结束循环。"><code>while</code></a></li>
<li><a href="Reference/Statements/for" title="for 语句用于创建一个循环，它包含了三个可选的表达式，三个可选的表达式包围在圆括号中并由分号分隔， 后跟一个在循环中执行的语句（通常是一个块语句）。"><code>for</code></a></li>
</ul>
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