uTools-Manuals/docs/javascript/Reference/Global_Objects/String/fromCodePoint.html

<article id="wikiArticle">
<div></div>
<p><strong><code>String.fromCodePoint()</code> 静态方法返回使用指定的代码点序列创建的字符串。</strong></p>
<div><iframe class="interactive interactive-js" frameborder="0" height="250" src="https://interactive-examples.mdn.mozilla.net/pages/js/string-fromcodepoint.html" width="100%"></iframe></div>
<p class="hidden">The source for this interactive example is stored in a GitHub repository. If you'd like to contribute to the interactive examples 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>
<h2 id="语法">语法</h2>
<pre><code class="language-javascript"><code>String.fromCodePoint(<var>num1</var>[, ...[, <var>numN</var>]])</code></code></pre>
<h3 id="参数">参数</h3>
<dl>
<dt><code>num1, ..., num<em>N</em></code></dt>
<dd>一串 Unicode 编码位置，即“代码点”。</dd>
<dt>
<h3 id="返回值">返回值</h3>
<p>使用指定的 Unicode 编码位置创建的字符串。</p>
</dt>
</dl>
<h3 id="异常">异常</h3>
<dl>
<dt><a href="Reference/Global_Objects/RangeError" title="RangeError对象标明一个错误，当一个值不在其所允许的范围或者集合中。"><code>RangeError</code></a></dt>
<dd>如果传入无效的 Unicode 编码，将会抛出一个<a href="Reference/Global_Objects/RangeError" title="RangeError对象标明一个错误，当一个值不在其所允许的范围或者集合中。"><code>RangeError</code></a> (例如： "RangeError: NaN is not a valid code point")。</dd>
</dl>
<h2 id="说明">说明</h2>
<p>该方法返回一个字符串，而不是一个 <a href="Reference/String" title="此页面仍未被本地化, 期待您的翻译!"><code>String</code></a> 对象。</p>
<p>因为 <code>fromCodePoint()</code> 是 <a href="Reference/String" title="此页面仍未被本地化, 期待您的翻译!"><code>String</code></a> 的一个静态方法，所以只能通过 <code>String.fromCodePoint()</code> 这样的方式来使用，不能在你创建的 <a href="Reference/String" title="此页面仍未被本地化, 期待您的翻译!"><code>String</code></a> 对象实例上直接调用。</p>
<h2 id="例子">例子</h2>
<h3 id="使用_fromCodePoint()">使用 <code>fromCodePoint()</code></h3>
<pre><code  class="language-javascript">String.fromCodePoint(42);       // "*"
String.fromCodePoint(65, 90);   // "AZ"
String.fromCodePoint(0x404);    // "\u0404"
String.fromCodePoint(0x2F804);  // "\uD87E\uDC04"
String.fromCodePoint(194564);   // "\uD87E\uDC04"
String.fromCodePoint(0x1D306, 0x61, 0x1D307) // "\uD834\uDF06a\uD834\uDF07"

String.fromCodePoint('_');      // RangeError
String.fromCodePoint(Infinity); // RangeError
String.fromCodePoint(-1);       // RangeError
String.fromCodePoint(3.14);     // RangeError
String.fromCodePoint(3e-2);     // RangeError
String.fromCodePoint(NaN);      // RangeError
</code></pre>
<pre><code  class="language-javascript">// String.fromCharCode() 方法不能单独获取在高代码点位上的字符
// 另一方面，下列的示例中，可以返回 4 字节，也可以返回 2 字节的字符
// (也就是说，它可以返回单独的字符，使用长度 2 代替 1!） 
console.log(String.fromCodePoint(0x2F804)); // or 194564 in decimal
</code></pre>
<h2 id="Polyfill">Polyfill</h2>
<p><code>String.fromCodePoint</code> 方法是 ECMAScript2015（ES6）新增加的特性，所以一些老的浏览器可能还不支持。可以通过使用下面的 polyfill 代码来保证浏览器的支持：</p>
<pre><code  class="language-javascript">if (!String.fromCodePoint) (function(stringFromCharCode) {
    var fromCodePoint = function(_) {
      var codeUnits = [], codeLen = 0, result = "";
      for (var index=0, len = arguments.length; index !== len; ++index) {
        var codePoint = +arguments[index];
        // correctly handles all cases including `NaN`, `-Infinity`, `+Infinity`
        // The surrounding `!(...)` is required to correctly handle `NaN` cases
        // The (codePoint&gt;&gt;&gt;0) === codePoint clause handles decimals and negatives
        if (!(codePoint &lt; 0x10FFFF &amp;&amp; (codePoint&gt;&gt;&gt;0) === codePoint))
          throw RangeError("Invalid code point: " + codePoint);
        if (codePoint &lt;= 0xFFFF) { // BMP code point
          codeLen = codeUnits.push(codePoint);
        } else { // Astral code point; split in surrogate halves
          // https://mathiasbynens.be/notes/javascript-encoding#surrogate-formulae
          codePoint -= 0x10000;
          codeLen = codeUnits.push(
            (codePoint &gt;&gt; 10) + 0xD800,  // highSurrogate
            (codePoint % 0x400) + 0xDC00 // lowSurrogate
          );
        }
        if (codeLen &gt;= 0x3fff) {
          result += stringFromCharCode.apply(null, codeUnits);
          codeUnits.length = 0;
        }
      }
      return result + stringFromCharCode.apply(null, codeUnits);
    };
    try { // IE 8 only supports `Object.defineProperty` on DOM elements
      Object.defineProperty(String, "fromCodePoint", {
        "value": fromCodePoint, "configurable": true, "writable": true
      });
    } catch(e) {
      String.fromCodePoint = fromCodePoint;
    }
}(String.fromCharCode));
</code></pre>
<h2 id="规范">规范</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">规范</th>
<th scope="col">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-string.fromcodepoint" hreflang="en" lang="en" rel="noopener">ECMAScript 2015 (6th Edition, ECMA-262)<br/><small lang="zh-CN">String.fromCodePoint</small></a></td>
<td><span class="spec-Standard">Standard</span></td>
<td>Initial definition.</td>
</tr>
<tr>
<td><a class="external" href="https://tc39.github.io/ecma262/#sec-string.fromcodepoint" hreflang="en" lang="en" rel="noopener">ECMAScript Latest Draft (ECMA-262)<br/><small lang="zh-CN">String.fromCodePoint</small></a></td>
<td><span class="spec-Draft">Draft</span></td>
<td> </td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<p 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.</p>
<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>fromCodePoint</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>
              41</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>
              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">
<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>
              28</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>
              10</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>
              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">
<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>
              10</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 bc-has-history"><span class="bc-browser-name">nodejs</span><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              4.0.0<div class="bc-icons"></div><section class="bc-history" id="sect1"><dl><dt class="bc-supports-yes bc-supports"><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              4.0.0<div class="bc-icons"></div></dt><dd></dd><dt class="bc-supports-yes bc-supports"><abbr class="bc-level-yes only-icon" title="Full support">
<span>Full support</span>
</abbr>
              0.12<div class="bc-icons"><abbr class="only-icon" title="User must explicitly enable this feature."><span>Disabled</span><i class="ic-disabled"></i></abbr> </div></dt><dd><abbr class="only-icon" title="User must explicitly enable this feature."><span>Disabled</span><i class="ic-disabled"></i></abbr> From version 0.12: this feature is behind the <code>--harmony</code> runtime flag.</dd></dl></section></td></tr></tbody></table><section class="bc-legend" id="sect2"><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><dt><abbr class="only-icon" title="User must explicitly enable this feature."><span>User must explicitly enable this feature.</span><i class="ic-disabled"></i></abbr></dt><dd>User must explicitly enable this feature.</dd></dl></section></div><p></p>
<h2 id="参见">参见</h2>
<ul>
<li><a href="Reference/Global_Objects/String/fromCharCode" title="静态 String.fromCharCode() 方法返回由指定的UTF-16代码单元序列创建的字符串。"><code>String.fromCharCode()</code></a></li>
<li><a href="Reference/Global_Objects/String/charAt" title="charAt() 方法从一个字符串中返回指定的字符。"><code>String.prototype.charAt()</code></a></li>
<li><a href="Reference/Global_Objects/String/codePointAt" title="codePointAt() 方法返回 一个 Unicode 编码点值的非负整数。"><code>String.prototype.codePointAt()</code></a></li>
<li><a href="Reference/Global_Objects/String/charCodeAt" title="charCodeAt() 方法返回0到65535之间的整数，表示给定索引处的UTF-16代码单元 (在 Unicode 编码单元表示一个单一的 UTF-16 编码单元的情况下，UTF-16 编码单元匹配 Unicode 编码单元。但在——例如 Unicode 编码单元 &gt; 0x10000 的这种——不能被一个 UTF-16 编码单元单独表示的情况下，只能匹配 Unicode 代理对的第一个编码单元) 。如果你想要整个代码点的值，使用 codePointAt()。"><code>String.prototype.charCodeAt()</code></a></li>
</ul>
</article>