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225 lines
16 KiB
HTML
<article id="wikiArticle">
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<div></div>
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<p><code><strong>Promise.all(iterable)</strong></code> 方法返回一个 <a href="Reference/Global_Objects/Promise" title="Promise 对象用于表示一个异步操作的最终状态（完成或失败），以及该异步操作的结果值。"><code>Promise</code></a> 实例，此实例在 <code>iterable</code> 参数内所有的 <code>promise</code> 都“完成（resolved）”或参数中不包含 <code>promise</code> 时回调完成（resolve）；如果参数中 <code>promise</code> 有一个失败（rejected），此实例回调失败（reject），失败原因的是第一个失败 <code>promise</code> 的结果。</p>
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<div><iframe class="interactive interactive-js" frameborder="0" height="250" src="https://interactive-examples.mdn.mozilla.net/pages/js/promise-all.html" width="100%"></iframe></div>
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<p class="hidden">The source for this interactive demo is stored in a GitHub repository. If you'd like to contribute to the interactive demo project, please clone <a class="external" href="https://github.com/mdn/interactive-examples" rel="noopener">https://github.com/mdn/interactive-examples</a> and send us a pull request.</p>
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<h2 id="语法">语法</h2>
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<pre><code class="language-javascript"><var>Promise.all(iterable)</var>;</code></pre>
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<h3 id="参数">参数</h3>
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<dl>
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<dt>iterable</dt>
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<dd>一个<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterable_protocol">可迭代</a>对象，如 <a href="Reference/Array" title="REDIRECT Array"><code>Array</code></a> 或 <a href="Reference/String" title="此页面仍未被本地化, 期待您的翻译!"><code>String</code></a>。</dd>
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</dl>
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<h3 id="返回值">返回值</h3>
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<ul>
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<li>如果传入的参数是一个空的可迭代对象，则返回一个<strong>已完成（already resolved）</strong>状态的 <a href="Reference/Global_Objects/Promise" title="Promise 对象用于表示一个异步操作的最终状态（完成或失败），以及该异步操作的结果值。"><code>Promise</code></a>。</li>
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<li>如果传入的参数不包含任何 <code>promise</code>，则返回一个<strong>异步完成（asynchronously resolved）</strong> <a href="Reference/Global_Objects/Promise" title="Promise 对象用于表示一个异步操作的最终状态（完成或失败），以及该异步操作的结果值。"><code>Promise</code></a>。注意：Google Chrome 58 在这种情况下返回一个<strong>已完成（already resolved）</strong>状态的 <a href="Reference/Global_Objects/Promise" title="Promise 对象用于表示一个异步操作的最终状态（完成或失败），以及该异步操作的结果值。"><code>Promise</code></a>。</li>
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<li>其它情况下返回一个<strong>处理中（pending）</strong>的<a href="Reference/Global_Objects/Promise" title="Promise 对象用于表示一个异步操作的最终状态（完成或失败），以及该异步操作的结果值。"><code>Promise</code></a>。这个返回的 <code>promise</code> 之后会在所有的 <code>promise</code> 都完成或有一个 <code>promise</code> 失败时<strong>异步</strong>地变为完成或失败。 见下方关于“Promise.all 的异步或同步”示例。返回值将会按照参数内的 <code>promise</code> 顺序排列，而不是由调用 <code>promise</code> 的完成顺序决定。</li>
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</ul>
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<h2 id="说明">说明</h2>
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<p>此方法在集合多个 <code>promise</code> 的返回结果时很有用。</p>
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<p>完成（Fulfillment）：<br/>
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如果传入的可迭代对象为空，<code>Promise.all</code> 会同步地返回一个已完成（resolved）状态的<code>promise</code>。<br/>
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如果所有传入的 <code>promise</code> 都变为完成状态，或者传入的可迭代对象内没有 <code>promise</code>，<code>Promise.all</code> 返回的 <code>promise</code> 异步地变为完成。<br/>
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在任何情况下，<code>Promise.all</code> 返回的 <code>promise</code> 的完成状态的结果都是一个数组，它包含所有的传入迭代参数对象的值（也包括非 <code>promise</code> 值）。</p>
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<p>失败/拒绝（Rejection）：<br/>
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如果传入的 <code>promise</code> 中有一个失败（rejected），<code>Promise.all</code> 异步地将失败的那个结果给失败状态的回调函数，而不管其它 <code>promise</code> 是否完成。</p>
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<h2 id="示例">示例</h2>
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<h3 id="Promise.all_的使用"><code>Promise.all</code> 的使用</h3>
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<p><code>Promise.all</code> 等待所有都完成（或第一个失败）。</p>
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<pre><code class="language-javascript">var p1 = Promise.resolve(3);
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var p2 = 1337;
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var p3 = new Promise((resolve, reject) => {
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setTimeout(resolve, 100, 'foo');
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});
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Promise.all([p1, p2, p3]).then(values => {
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console.log(values); // [3, 1337, "foo"]
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});</code></pre>
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<p>如果参数中包含非 <code>promise</code> 值，这些值将被忽略，但仍然会被放在返回数组中（如果 <code>promise</code> 完成的话）：</p>
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<pre><code class="language-javascript">// this will be counted as if the iterable passed is empty, so it gets fulfilled
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var p = Promise.all([1,2,3]);
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// this will be counted as if the iterable passed contains only the resolved promise with value "444", so it gets fulfilled
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var p2 = Promise.all([1,2,3, Promise.resolve(444)]);
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// this will be counted as if the iterable passed contains only the rejected promise with value "555", so it gets rejected
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var p3 = Promise.all([1,2,3, Promise.reject(555)]);
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// using setTimeout we can execute code after the stack is empty
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setTimeout(function(){
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console.log(p);
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console.log(p2);
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console.log(p3);
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});
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// logs
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// Promise { <state>: "fulfilled", <value>: Array[3] }
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// Promise { <state>: "fulfilled", <value>: Array[4] }
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// Promise { <state>: "rejected", <reason>: 555 }</code></pre>
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<h3 id="Promise.all_的异步和同步"><code>Promise.all</code> 的异步和同步</h3>
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<p>下面的例子中演示了 <code>Promise.all</code> 的异步性（如果传入的可迭代对象是空的，就是同步）：</p>
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<pre><code class="language-javascript">// we are passing as argument an array of promises that are already resolved,
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// to trigger Promise.all as soon as possible
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var resolvedPromisesArray = [Promise.resolve(33), Promise.resolve(44)];
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var p = Promise.all(resolvedPromisesArray);
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// immediately logging the value of p
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console.log(p);
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// using setTimeout we can execute code after the stack is empty
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setTimeout(function(){
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console.log('the stack is now empty');
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console.log(p);
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});
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// logs, in order:
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// Promise { <state>: "pending" }
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// the stack is now empty
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// Promise { <state>: "fulfilled", <value>: Array[2] }
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</code></pre>
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<p>如果 <code>Promise.all</code> 失败，也是一样的：</p>
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<pre><code class="language-javascript">var mixedPromisesArray = [Promise.resolve(33), Promise.reject(44)];
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var p = Promise.all(mixedPromisesArray);
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console.log(p);
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setTimeout(function(){
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console.log('the stack is now empty');
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console.log(p);
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});
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// logs
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// Promise { <state>: "pending" }
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// the stack is now empty
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// Promise { <state>: "rejected", <reason>: 44 }
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</code></pre>
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<p>但是，<code>Promise.all</code> <strong>当且仅当</strong>传入的可迭代对象为空时为同步：</p>
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<pre><code class="language-javascript">var p = Promise.all([]); // will be immediately resolved
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var p2 = Promise.all([1337, "hi"]); // non-promise values will be ignored, but the evaluation will be done asynchronously
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console.log(p);
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console.log(p2)
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setTimeout(function(){
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console.log('the stack is now empty');
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console.log(p2);
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});
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// logs
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// Promise { <state>: "fulfilled", <value>: Array[0] }
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// Promise { <state>: "pending" }
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// the stack is now empty
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// Promise { <state>: "fulfilled", <value>: Array[2] }
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</code></pre>
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<h3 id="Promise.all_的快速返回失败行为"><code>Promise.all</code> 的快速返回失败行为</h3>
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<p><code>Promise.all</code> 在任意一个传入的 <code>promise</code> 失败时返回失败。例如，如果你传入的 <code>promise</code>中，有四个 <code>promise</code> 在一定的时间之后调用成功函数，有一个立即调用失败函数，那么 <code>Promise.all</code> 将立即变为失败。</p>
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<pre><code class="language-javascript">var p1 = new Promise((resolve, reject) => {
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setTimeout(resolve, 1000, 'one');
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});
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var p2 = new Promise((resolve, reject) => {
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setTimeout(resolve, 2000, 'two');
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});
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var p3 = new Promise((resolve, reject) => {
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setTimeout(resolve, 3000, 'three');
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});
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var p4 = new Promise((resolve, reject) => {
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setTimeout(resolve, 4000, 'four');
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});
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var p5 = new Promise((resolve, reject) => {
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reject('reject');
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});
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Promise.all([p1, p2, p3, p4, p5]).then(values => {
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console.log(values);
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}, reason => {
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console.log(reason)
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});
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//From console:
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//"reject"
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//You can also use .catch
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Promise.all([p1, p2, p3, p4, p5]).then(values => {
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console.log(values);
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}).catch(reason => {
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console.log(reason)
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});
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//From console:
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//"reject"
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</code></pre>
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<h2 id="技术规范">技术规范</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">Specification</th>
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<th scope="col">Status</th>
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<th scope="col">Comment</th>
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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-promise.all" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">Promise.all</small></a></td>
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<td><span class="spec-Standard">Standard</span></td>
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<td>Initial definition in an ECMA standard.</td>
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</tr>
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<tr>
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<td><a class="external" href="https://tc39.github.io/ecma262/#sec-promise.all" hreflang="en" lang="en" rel="noopener">ECMAScript Latest Draft (ECMA-262)<br/><small lang="zh-CN">Promise.all</small></a></td>
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<td><span class="spec-Draft">Draft</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 class="hidden">To contribute to this compatibility data, please write a pull request against this repository: <a class="external" href="https://github.com/mdn/browser-compat-data" rel="noopener">https://github.com/mdn/browser-compat-data</a>.</p>
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<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>all</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">
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<span>Full support</span>
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</abbr>
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32</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">
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<span>Full support</span>
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</abbr>
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12</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">
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<span>Full support</span>
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</abbr>
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29</td><td class="bc-supports-no bc-browser-ie"><span class="bc-browser-name">IE</span><abbr class="bc-level-no only-icon" title="No support">
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<span>No support</span>
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</abbr>
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No</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">
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<span>Full support</span>
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</abbr>
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19</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">
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<span>Full support</span>
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</abbr>
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8</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">
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<span>Full support</span>
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</abbr>
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4.4.3</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">
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<span>Full support</span>
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</abbr>
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32</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">
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<span>Full support</span>
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</abbr>
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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">
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<span>Full support</span>
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</abbr>
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29</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">
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<span>Full support</span>
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</abbr>
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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">
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<span>Full support</span>
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</abbr>
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8</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">
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<span>Full support</span>
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</abbr>
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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">
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<span>Full support</span>
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</abbr>
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0.12</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">
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<abbr class="bc-level bc-level-yes only-icon" title="Full support">
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<span>Full support</span>
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</abbr></span></dt><dd>Full support</dd><dt><span class="bc-supports-no bc-supports">
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<abbr class="bc-level bc-level-no only-icon" title="No support">
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<span>No support</span>
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</abbr></span></dt><dd>No support</dd></dl></section></div><p></p>
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<h2 id="参见">参见</h2>
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<ul>
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<li><a href="Reference/Global_Objects/Promise" title="Promise 对象用于表示一个异步操作的最终状态（完成或失败），以及该异步操作的结果值。"><code>Promise</code></a></li>
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<li><a href="Reference/Global_Objects/Promise/race" title="Promise.race(iterable) 方法返回一个 promise，一旦迭代器中的某个promise解决或拒绝，返回的 promise就会解决或拒绝。"><code>Promise.race()</code></a></li>
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</ul>
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</article> |