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175 lines
11 KiB
HTML
<article id="wikiArticle">
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<div></div>
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<p><code><strong>entries()</strong></code> 方法返回一个新的<strong>Array Iterator</strong>对象，该对象包含数组中每个索引的键/值对。</p>
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<p><iframe class="interactive interactive-js" frameborder="0" height="250" src="https://interactive-examples.mdn.mozilla.net/pages/js/array-entries.html" width="100%"></iframe></p>
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<h2 id="语法">语法</h2>
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<pre class="syntaxbox"><code><em>arr</em>.entries()</code></pre>
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<h3 id="返回值">返回值</h3>
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<p>一个新的 <a href="Reference/Array" title="REDIRECT Array"><code>Array</code></a> 迭代器对象。<a class="external" href="http://www.ecma-international.org/ecma-262/6.0/#sec-createarrayiterator" rel="noopener">Array Iterator</a>是对象，它的原型（__proto__:Array Iterator）上有一个<a class="external" href="http://www.ecma-international.org/ecma-262/6.0/#sec-%arrayiteratorprototype%.next" rel="noopener">next</a>方法，可用用于遍历迭代器取得原数组的[key,value]。</p>
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<h2 id="示例">示例</h2>
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<h3 id="1、_Array_Iterator">1、 Array Iterator</h3>
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<pre class="brush: js">var arr = ["a", "b", "c"];
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var iterator = arr.entries();
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console.log(iterator);
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/*<em>Array Iterator {}</em>
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__proto__:Array Iterator
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next:<em>ƒ next()</em>
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Symbol(Symbol.toStringTag):"Array Iterator"
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__proto__:<em>Object</em>
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*/</pre>
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<h3 id="2、iterator.next()">2、iterator.next()</h3>
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<pre class="brush: js">var arr = ["a", "b", "c"];
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var iterator = arr.entries();
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console.log(iterator.next());
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/*{value: Array(2), done: false}
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done:false
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value:(2) [0, "a"]
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__proto__: Object
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*/
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// iterator.next()返回一个对象，对于有元素的数组，
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// 是next{ value: Array(2), done: false }；
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// next.done 用于指示迭代器是否完成：在每次迭代时进行更新而且都是false，
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// 直到迭代器结束done才是true。
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// next.value是一个["key":"value"]的数组，是返回的迭代器中的元素值。
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</pre>
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<h3 id="3、iterator.next方法运行">3、iterator.next方法运行</h3>
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<pre class="brush: js">var arr = ["a", "b", "c"];
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var iter = arr.entries();
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var a = [];
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// for(var i=0; i< arr.length; i++){ // 实际使用的是这个
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for(var i=0; i< arr.length+1; i++){ // 注意，是length+1，比数组的长度大
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var tem = iter.next(); // 每次迭代时更新next
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console.log(tem.done); // 这里可以看到更新后的done都是false
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if(tem.done !== true){ // 遍历迭代器结束done才是true
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console.log(tem.value);
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a[i]=tem.value;
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}
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}
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console.log(a); // 遍历完毕，输出next.value的数组</pre>
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<h3 id="4、二维数组按行排序">4、二维数组按行排序</h3>
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<pre class="brush: js">function sortArr(arr) {
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var goNext = true;
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var entries = arr.entries();
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while (goNext) {
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var result = entries.next();
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if (result.done !== true) {
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result.value[1].sort((a, b) => a - b);
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goNext = true;
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} else {
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goNext = false;
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}
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}
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return arr;
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}
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var arr = [[1,34],[456,2,3,44,234],[4567,1,4,5,6],[34,78,23,1]];
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sortArr(arr);
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/*(4) [Array(2), Array(5), Array(5), Array(4)]
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0:(2) [1, 34]
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1:(5) [2, 3, 44, 234, 456]
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2:(5) [1, 4, 5, 6, 4567]
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3:(4) [1, 23, 34, 78]
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length:4
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__proto__:Array(0)
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*/
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</pre>
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<h3 id="5、使用for…of_循环">5、使用<a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of">for…of</a> 循环</h3>
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<pre class="brush:js">var arr = ["a", "b", "c"];
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var iterator = arr.entries();
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// undefined
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for (let e of iterator) {
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console.log(e);
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}
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// [0, "a"]
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// [1, "b"]
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// [2, "c"]
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</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">规范名称</th>
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<th scope="col">规范状态</th>
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<th scope="col">备注</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-array.prototype.entries" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">Array.prototype.entries</small></a></td>
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<td><span class="spec-Standard">Standard</span></td>
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<td>首次定义</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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<div>
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<div>
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<div class="hidden">The compatibility table in 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>
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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>entries</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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38</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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28</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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25</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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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">
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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-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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28</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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</div>
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</div>
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<h2 id="相关链接">相关链接</h2>
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<ul>
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<li><a href="Reference/Global_Objects/Array/keys" title="keys() 方法返回一个包含数组中每个索引键的Array Iterator对象。"><code>Array.prototype.keys()</code></a></li>
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<li><a href="Reference/Global_Objects/Array/forEach" title="forEach() 方法对数组的每个元素执行一次提供的函数。"><code>Array.prototype.forEach()</code></a></li>
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<li><a href="Reference/Global_Objects/Array/every" title="every() 方法测试数组的所有元素是否都通过了指定函数的测试。"><code>Array.prototype.every()</code></a></li>
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<li><a href="Reference/Global_Objects/Array/some" title="some() 方法测试是否至少有一个元素通过由提供的函数实现的测试。"><code>Array.prototype.some()</code></a></li>
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<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of">for...of</a></li>
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<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols">Iteration protocols</a></li>
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</ul>
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</article> |