uTools-Manuals/docs/javascript/Reference/Global_Objects/Array/entries.html

<article id="wikiArticle">
<div></div>
<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>
<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>
<h2 id="语法">语法</h2>
<pre><code class="language-javascript"><code><em>arr</em>.entries()</code></code></pre>
<h3 id="返回值">返回值</h3>
<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>
<h2 id="示例">示例</h2>
<h3 id="1、_Array_Iterator">1、 Array Iterator</h3>
<pre><code  class="language-javascript">var arr = ["a", "b", "c"];
var iterator = arr.entries();
console.log(iterator);

/*<em>Array Iterator {}</em>
         __proto__:Array Iterator
         next:<em>ƒ next()</em>
         Symbol(Symbol.toStringTag):"Array Iterator"
         __proto__:<em>Object</em>
*/</code></pre>
<h3 id="2、iterator.next()">2、iterator.next()</h3>
<pre><code  class="language-javascript">var arr = ["a", "b", "c"]; 
var iterator = arr.entries();
console.log(iterator.next());

/*{value: Array(2), done: false}
          done:false
          value:(2) [0, "a"]
           __proto__: Object
*/
// iterator.next()返回一个对象，对于有元素的数组，
// 是next{ value: Array(2), done: false }；
// 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，
// 直到迭代器结束done才是true。
// next.value是一个["key":"value"]的数组，是返回的迭代器中的元素值。
</code></pre>
<h3 id="3、iterator.next方法运行">3、iterator.next方法运行</h3>
<pre><code  class="language-javascript">var arr = ["a", "b", "c"];
var iter = arr.entries();
var a = [];

// for(var i=0; i&lt; arr.length; i++){   // 实际使用的是这个 
for(var i=0; i&lt; arr.length+1; i++){    // 注意，是length+1，比数组的长度大
    var tem = iter.next();             // 每次迭代时更新next
    console.log(tem.done);             // 这里可以看到更新后的done都是false
    if(tem.done !== true){             // 遍历迭代器结束done才是true
        console.log(tem.value);
        a[i]=tem.value;
    }
}
    
console.log(a);                         // 遍历完毕，输出next.value的数组</code></pre>
<h3 id="4、二维数组按行排序">4、二维数组按行排序</h3>
<pre><code  class="language-javascript">function sortArr(arr) {
    var goNext = true;
    var entries = arr.entries();
    while (goNext) {
        var result = entries.next();
        if (result.done !== true) {
            result.value[1].sort((a, b) =&gt; a - b);
            goNext = true;
        } else {
            goNext = false;
        }
    }
    return arr;
}

var arr = [[1,34],[456,2,3,44,234],[4567,1,4,5,6],[34,78,23,1]];
sortArr(arr);

/*(4) [Array(2), Array(5), Array(5), Array(4)]
    0:(2) [1, 34]
    1:(5) [2, 3, 44, 234, 456]
    2:(5) [1, 4, 5, 6, 4567]
    3:(4) [1, 23, 34, 78]
    length:4
    __proto__:Array(0)
*/
</code></pre>
<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>
<pre><code class="language-js">var arr = ["a", "b", "c"];
var iterator = arr.entries();
// undefined

for (let e of iterator) {
    console.log(e);
}

// [0, "a"] 
// [1, "b"] 
// [2, "c"]
</code></pre>
<h2 id="规范">规范</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">规范名称</th>
<th scope="col">规范状态</th>
<th scope="col">备注</th>
</tr>
<tr>
<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>
<td><span class="spec-Standard">Standard</span></td>
<td>首次定义</td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<div>
<div>
<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>
<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">
<span>Full support</span>
</abbr>
              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">
<span>Full support</span>
</abbr>
              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">
<span>Full support</span>
</abbr>
              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">
<span>No support</span>
</abbr>
              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">
<span>Full support</span>
</abbr>
              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">
<span>Full support</span>
</abbr>
              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">
<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>
              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">
<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>
              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">
<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>
              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">
<abbr class="bc-level bc-level-yes only-icon" title="Full support">
<span>Full support</span>
                  
                </abbr></span></dt><dd>Full support</dd><dt><span class="bc-supports-no bc-supports">
<abbr class="bc-level bc-level-no only-icon" title="No support">
<span>No support</span>
                  
                </abbr></span></dt><dd>No support</dd></dl></section></div><p></p>
</div>
</div>
<h2 id="相关链接">相关链接</h2>
<ul>
<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>
<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>
<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>
<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>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of">for...of</a></li>
<li><a href="https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols">Iteration protocols</a></li>
</ul>
</article>