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代码的常见问题</a></li><li><a href="/zh-CN/docs/Learn_web_development/Howto/Web_mechanics">Web 机制</a></li><li><a href="/zh-CN/docs/Learn_web_development/Howto/Tools_and_setup">工具和安装</a></li><li><a href="/zh-CN/docs/Learn_web_development/Howto/Design_and_accessibility">设计与无障碍</a></li></ol></details></li><li><a href="/en-US/docs/Learn_web_development/About" class="only-in-en-us">关于</a></li><li><a href="/en-US/docs/Learn_web_development/Educators" class="only-in-en-us">面向教育工作者的资源</a></li><li><a href="/en-US/docs/Learn_web_development/Changelog" class="only-in-en-us">更新日志</a></li></ol></div></div><section class="place side"></section></nav></aside><div class="toc-container"><aside class="toc"><nav><div class="document-toc-container"><section class="document-toc"><header><h2 class="document-toc-heading">在本文中</h2></header><ul class="document-toc-list"><li class="document-toc-item "><a class="document-toc-link" href="#什么是返回值？">什么是返回值？</a></li><li class="document-toc-item "><a class="document-toc-link" href="#主动学习：我们自己的返回值函数">主动学习：我们自己的返回值函数</a></li><li class="document-toc-item "><a class="document-toc-link" href="#结论">结论</a></li><li class="document-toc-item "><a class="document-toc-link" href="#参见">参见</a></li></ul></section></div></nav></aside><section class="place side"></section></div></div><main id="content" class="main-content "><article class="main-page-content" lang="zh-CN"><header><h1>函数返回值</h1></header><div class="section-content"><ul class="prev-next"><li><a class="button secondary" href="/zh-CN/docs/Learn_web_development/Core/Scripting/Build_your_own_function"><span class="button-wrap"> 上一页 </span></a></li><li><a class="button secondary" href="/zh-CN/docs/Learn_web_development/Core/Scripting"><span class="button-wrap"> 概述：创建 JavaScript 代码块</span></a></li><li><a class="button secondary" href="/zh-CN/docs/Learn_web_development/Core/Scripting/Events"><span class="button-wrap"> 下一页 </span></a></li></ul> <p>函数返回值 - 是本章中最后一个基础概念，让我们一起来瞧瞧.。有些函数在执行完毕后不会返回一个有用的值，但有些会，重要的是理解返回的是什么，怎样使用这些值在你的代码中，我们将在下面讨论这些。</p> <figure class="table-container"><table> <tbody> <tr> <th scope="row">前提：</th> <td> <p> 基础的计算机知识，懂得基础的 HTML 和 CSS, <a href="/zh-CN/docs/Learn_web_development/Core/Scripting">JavaScript </a>第一步学习，函数-<a href="/zh-CN/docs/Learn_web_development/Core/Scripting/Functions"> </a>可重用的代码块。 </p> </td> </tr> <tr> <th scope="row">目标：</th> <td>理解什么函数的返回值 , 和如何使用它们</td> </tr> </tbody> </table></figure></div><section aria-labelledby="什么是返回值？"><h2 id="什么是返回值？"><a href="#什么是返回值？">什么是返回值？</a></h2><div class="section-content"><p>返回值意如其名，是指函数执行完毕后返回的值。你已经多次遇见过返回值，尽管你可能没有明确的考虑过他们。让我们一起回看一些熟悉的代码：</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>var myText = "I am a string"; var newString = myText.replace("string", "sausage"); console.log(newString); // the replace() string function takes a string, // replaces one substring with another, and returns // a new string with the replacement made </code></pre></div> <p>在第一篇函数文章中，我们确切地看到了这一块代码。我们对 <code>myText</code> 字符串调用 <a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/String/replace">replace()</a> 功能，并通过这两个参数的字符串查找，和子串替换它。当这个函数完成（完成运行）后，它返回一个值，这个值是一个新的字符串，它具有替换的功能。在上面的代码中，我们保存这个返回值，以作为<code>newString</code>变量的内容。</p> <p>如果你看看替换功能 MDN 参考页面，你会看到一个<a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/String/replace#return_value">返回值</a>。知道和理解函数返回的值是非常有用的，因此我们尽可能地包含这些信息。</p> <p>一些函数没有返回值就像 (在我们的参考页中，返回值在这种情况下被列出为空值 <code>void</code> 或未定义值 <code>undefined</code> 。).例如，我们在前面文章中创建的 <a href="https://github.com/mdn/learning-area/blob/main/javascript/building-blocks/functions/function-stage-4.html#L50" class="external" target="_blank">displayMessage() function</a> , 由于调用的函数的结果，没有返回特定的值。它只是让一个提示框出现在屏幕的某个地方——就是这样！</p> <p>通常，返回值是用在函数在计算某种中间步骤。你想得到最终结果，其中包含一些值。那些值需要通过一个函数计算得到，然后返回结果可用于计算的下一个阶段。</p></div></section><section aria-labelledby="在自定义的函数中使用返回值"><h3 id="在自定义的函数中使用返回值"><a href="#在自定义的函数中使用返回值">在自定义的函数中使用返回值</a></h3><div class="section-content"><p>要从自定义函数返回值，你需要使用…等待它… <a href="/zh-CN/docs/Web/JavaScript/Reference/Statements/return">return</a> 关键字。我们最近在<a href="https://github.com/mdn/learning-area/blob/main/javascript/building-blocks/loops/random-canvas-circles.html" class="external" target="_blank">random-canvas-circles.html</a>示例中看到了这一点。我们的 <code>draw()</code> 函数绘制 100 随机圆在 HTML 的<a href="/zh-CN/docs/Web/HTML/Element/canvas"><code><canvas></code></a>:</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>function draw() { ctx.clearRect(0, 0, WIDTH, HEIGHT); for (var i = 0; i < 100; i++) { ctx.beginPath(); ctx.fillStyle = "rgba(255,0,0,0.5)"; ctx.arc(random(WIDTH), random(HEIGHT), random(50), 0, 2 * Math.PI); ctx.fill(); } } </code></pre></div> <p>在每个循环迭代，<code>random()</code>函数调用了三次，分别生成当前圆的 x 坐标，一个随机值 Y 坐标和半径。<code>random()</code>函数接受一个参数 - 一个整数，返回 0 到这个整数之间的随机数。看起来像这样：</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>function randomNumber(number) { return Math.floor(Math.random() * number); } </code></pre></div> <p>这也可以写成下面这样：</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>function randomNumber(number) { var result = Math.floor(Math.random() * number); return result; } </code></pre></div> <p>但是第一个版本写得更快，而且更紧凑。</p> <p>我们每次调用函数都返回<code>Math.floor(Math.random()*number)</code>计算的数学结果。这个返回值出现在调用函数的位置上，并且代码继续。例如，如果我们运行下面的行：</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>ctx.arc(random(WIDTH), random(HEIGHT), random(50), 0, 2 * Math.PI); </code></pre></div> <p>这三次<code>random()</code>调用分别返回值 500, 200 和 35，实际上这一行这样运行：</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>ctx.arc(500, 200, 35, 0, 2 * Math.PI); </code></pre></div> <p>在运行该行之前，首先运行该行上的函数调用，并用其返回值替换该函数调用。</p></div></section><section aria-labelledby="主动学习：我们自己的返回值函数"><h2 id="主动学习：我们自己的返回值函数"><a href="#主动学习：我们自己的返回值函数">主动学习：我们自己的返回值函数</a></h2><div class="section-content"><p>让我们着手编写具有我们自己的返回值的函数。</p> <ol> <li> <p>首先，从 GitHub 的<a href="https://github.com/mdn/learning-area/blob/main/javascript/building-blocks/functions/function-library.html" class="external" target="_blank">function-library.html</a>文件复制一份本地副本。这是一个简单的 HTML 页面包含一个 <a href="/zh-CN/docs/Web/HTML/Element/input"><code><input></code></a> 文本域和一个段落。还有一个 <a href="/zh-CN/docs/Web/HTML/Element/script"><code><script></code></a> 元素，我们在两个变量中存储了对两个 HTML 元素的引用。这个小页面允许你在文本框中输入一个数字，并在下面的段落中显示不同的数字。</p> </li> <li> <p>让我们添加一些有用的函数。在现有的两行 JavaScript 下面，添加以下函数定义：</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>function squared(num) { return num * num; } function cubed(num) { return num * num * num; } function factorial(num) { var x = num; while (x > 1) { num *= x - 1; x--; } return num; } </code></pre></div> <p><code>squared()</code> 和 <code>cubed()</code> 功能是相当明显的 - 他们的平方或立方的数作为一个参数返回。factorial() 函数返回给定数字的阶乘。</p> </li> <li> <p>接下来，我们将包括一种打印输入到文本输入中的数字的信息的方法。在现有函数下面输入以下事件处理程序：</p> <div class="code-example"><div class="example-header"><span class="language-name">js</span></div><pre class="brush: js notranslate"><code>input.onchange = function () { var num = input.value; if (isNaN(num)) { para.textContent = "You need to enter a number!"; } else { para.textContent = num + " squared is " + squared(num) + ". " + num + " cubed is " + cubed(num) + ". " + num + " factorial is " + factorial(num) + "."; } }; </code></pre></div> <p>这里我们创建一个<code>onchange</code>事件处理程序，当文本框上面的 change 事件被触发的之后，事件处理程序就会运行 - 就是说，一个新的值被输入到文本框并且被提交（就比如，输入一个值，然后按 Tab）。当这个匿名函数运行时，输入框中的值将被存储在<code>num</code>变量中。</p> <p>接下来，我们进行条件测试——如果输入的值不是数字，则在段落中打印错误消息。if 语句判断<a href="/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/isNaN">isNaN(num)</a>表达式是否返回 true。我们用<code>isNaN()</code>函数测试<code>num</code>的值是否不是一个数字 - 如果不是数字，就返回<code>true</code>，否则返回<code>false</code>。</p> <p>如果测试返回 false，则数值是一个数字，所以我们在段落元素中打印出一个句子，说明数字的平方、立方体和阶乘是什么。这句话叫 squared()，cubed()，和 factorial() 函数来获得所需的值。</p> </li> <li> <p>保存你的代码，将其加载到浏览器中，然后尝试。</p> </li> </ol> <div class="notecard note"> <p><strong>备注：</strong> 如果你有麻烦让例子工作，对比<a href="https://github.com/mdn/learning-area/blob/main/javascript/building-blocks/functions/function-library-finished.html" class="external" target="_blank">GitHub 的已完成版</a>检查你的代码（或<a href="https://mdn.github.io/learning-area/javascript/building-blocks/functions/function-library-finished.html" class="external" target="_blank">看它在线运行</a>），或寻求我们的帮助。</p> </div> <p>在这一点上，我们希望你编写一个自己的几个函数，并将它们添加到库中。这个数的平方根或立方根，或一个圆的周长和半径是多少？</p> <p>这个练习提出了一些重要的观点，除了研究如何使用返回语句之外。此外，我们还有：</p> <ul> <li>查看另一个将错误处理写入函数的示例。它是否提供了任何必要的参数通常是一个好主意，另一方面对可选参数提供默认值。这样，你的程序就不太可能出错了。</li> <li>关于创建函数库思想的思考。随着你深入到你的编程生涯，你将开始一次又一次地做同样的事情。这是一个好主意，开始保持你自己的实用工具库，你经常使用 - 你可以把它们复制到你的新代码，甚至只是把它应用到任何你需要的 HTML 页面。</li> </ul></div></section><section aria-labelledby="结论"><h2 id="结论"><a href="#结论">结论</a></h2><div class="section-content"><p>因此，我们让它 - 功能是有趣的，非常有用的，虽然有很多要谈论他们的语法和功能，相当容易理解的正确的文章学习。</p> <p>如果你有什么不明白的地方，可以再通读一遍，或者<a href="/zh-CN/docs/Learn_web_development#contact_us">联系我们</a>寻求帮助。</p></div></section><section aria-labelledby="参见"><h2 id="参见"><a href="#参见">参见</a></h2><div class="section-content"><ul> <li><a href="/zh-CN/docs/Web/JavaScript/Reference/Functions">Functions in-depth</a> — 详细介绍更多高级功能相关信息的指南。</li> <li><a href="https://www.impressivewebs.com/callback-functions-javascript/" class="external" target="_blank">Callback functions in JavaScript</a> — 一个常见的 JavaScript 模式是把一个函数传递给另一个函数作为参数，然后在第一个函数中调用它。这有点超出了这门课的范围，但值得学习很久。</li> </ul> <ul class="prev-next"><li><a class="button secondary" href="/zh-CN/docs/Learn_web_development/Core/Scripting/Build_your_own_function"><span class="button-wrap"> 上一页 </span></a></li><li><a class="button secondary" href="/zh-CN/docs/Learn_web_development/Core/Scripting"><span class="button-wrap"> 概述：创建 JavaScript 代码块</span></a></li><li><a class="button secondary" href="/zh-CN/docs/Learn_web_development/Core/Scripting/Events"><span class="button-wrap"> 下一页 </span></a></li></ul></div></section></article><aside class="article-footer"><div class="article-footer-inner"><div class="svg-container"><svg xmlns="http://www.w3.org/2000/svg" width="162" height="162" viewBox="0 0 162 162" fill="none" role="none"><mask id="b" fill="#fff"><path 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noreferrer">Website Privacy Notice</a></li><li class="footer-moz-item"><a href="https://www.mozilla.org/privacy/websites/#cookies" class="footer-moz-link" target="_blank" rel="noopener noreferrer">Cookies</a></li><li class="footer-moz-item"><a href="https://www.mozilla.org/about/legal/terms/mozilla" class="footer-moz-link" target="_blank" rel="noopener noreferrer">Legal</a></li><li class="footer-moz-item"><a href="https://www.mozilla.org/about/governance/policies/participation/" class="footer-moz-link" target="_blank" rel="noopener noreferrer">Community Participation Guidelines</a></li></ul></div><div class="page-footer-legal"><p id="license" class="page-footer-legal-text">Visit <a href="https://www.mozilla.org" target="_blank" rel="noopener noreferrer">Mozilla Corporation’s</a> not-for-profit parent, the <a target="_blank" rel="noopener noreferrer" href="https://foundation.mozilla.org/">Mozilla Foundation</a>.<br/>Portions of this content are ©1998–2025 by individual mozilla.org contributors. Content available under <a href="/zh-CN/docs/MDN/Writing_guidelines/Attrib_copyright_license">a Creative Commons license</a>.</p></div></div></footer></div><script type="application/json" id="hydration">{"url":"/zh-CN/docs/Learn_web_development/Core/Scripting/Return_values","doc":{"body":[{"type":"prose","value":{"id":null,"title":null,"isH3":false,"content":"<ul class=\"prev-next\"><li><a class=\"button secondary\" href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Build_your_own_function\"><span class=\"button-wrap\"> 上一页 </span></a></li><li><a class=\"button secondary\" href=\"/zh-CN/docs/Learn_web_development/Core/Scripting\"><span class=\"button-wrap\"> 概述：创建 JavaScript 代码块</span></a></li><li><a class=\"button secondary\" href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Events\"><span class=\"button-wrap\"> 下一页 </span></a></li></ul>\n<p>函数返回值 - 是本章中最后一个基础概念，让我们一起来瞧瞧.。有些函数在执行完毕后不会返回一个有用的值，但有些会，重要的是理解返回的是什么，怎样使用这些值在你的代码中，我们将在下面讨论这些。</p>\n<figure class=\"table-container\"><table>\n <tbody>\n <tr>\n <th scope=\"row\">前提：</th>\n <td>\n <p>\n 基础的计算机知识，懂得基础的 HTML 和 CSS,\n <a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting\">JavaScript </a>第一步学习，函数-<a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Functions\">\n </a>可重用的代码块。\n </p>\n </td>\n </tr>\n <tr>\n <th scope=\"row\">目标：</th>\n <td>理解什么函数的返回值 , 和如何使用它们</td>\n </tr>\n </tbody>\n</table></figure>"}},{"type":"prose","value":{"id":"什么是返回值？","title":"什么是返回值？","isH3":false,"content":"<p>返回值意如其名，是指函数执行完毕后返回的值。你已经多次遇见过返回值，尽管你可能没有明确的考虑过他们。让我们一起回看一些熟悉的代码：</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>var myText = \"I am a string\";\nvar newString = myText.replace(\"string\", \"sausage\");\nconsole.log(newString);\n// the replace() string function takes a string,\n// replaces one substring with another, and returns\n// a new string with the replacement made\n</code></pre></div>\n<p>在第一篇函数文章中，我们确切地看到了这一块代码。我们对 <code>myText</code> 字符串调用 <a href=\"/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/String/replace\">replace()</a> 功能，并通过这两个参数的字符串查找，和子串替换它。当这个函数完成（完成运行）后，它返回一个值，这个值是一个新的字符串，它具有替换的功能。在上面的代码中，我们保存这个返回值，以作为<code>newString</code>变量的内容。</p>\n<p>如果你看看替换功能 MDN 参考页面，你会看到一个<a href=\"/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/String/replace#return_value\">返回值</a>。知道和理解函数返回的值是非常有用的，因此我们尽可能地包含这些信息。</p>\n<p>一些函数没有返回值就像 (在我们的参考页中，返回值在这种情况下被列出为空值 <code>void</code> 或未定义值 <code>undefined</code> 。).例如，我们在前面文章中创建的 <a href=\"https://github.com/mdn/learning-area/blob/main/javascript/building-blocks/functions/function-stage-4.html#L50\" class=\"external\" target=\"_blank\">displayMessage() function</a> , 由于调用的函数的结果，没有返回特定的值。它只是让一个提示框出现在屏幕的某个地方——就是这样！</p>\n<p>通常，返回值是用在函数在计算某种中间步骤。你想得到最终结果，其中包含一些值。那些值需要通过一个函数计算得到，然后返回结果可用于计算的下一个阶段。</p>"}},{"type":"prose","value":{"id":"在自定义的函数中使用返回值","title":"在自定义的函数中使用返回值","isH3":true,"content":"<p>要从自定义函数返回值，你需要使用…等待它… <a href=\"/zh-CN/docs/Web/JavaScript/Reference/Statements/return\">return</a> 关键字。我们最近在<a href=\"https://github.com/mdn/learning-area/blob/main/javascript/building-blocks/loops/random-canvas-circles.html\" class=\"external\" target=\"_blank\">random-canvas-circles.html</a>示例中看到了这一点。我们的 <code>draw()</code> 函数绘制 100 随机圆在 HTML 的<a href=\"/zh-CN/docs/Web/HTML/Element/canvas\"><code><canvas></code></a>:</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>function draw() {\n ctx.clearRect(0, 0, WIDTH, HEIGHT);\n for (var i = 0; i < 100; i++) {\n ctx.beginPath();\n ctx.fillStyle = \"rgba(255,0,0,0.5)\";\n ctx.arc(random(WIDTH), random(HEIGHT), random(50), 0, 2 * Math.PI);\n ctx.fill();\n }\n}\n</code></pre></div>\n<p>在每个循环迭代，<code>random()</code>函数调用了三次，分别生成当前圆的 x 坐标，一个随机值 Y 坐标和半径。<code>random()</code>函数接受一个参数 - 一个整数，返回 0 到这个整数之间的随机数。看起来像这样：</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>function randomNumber(number) {\n return Math.floor(Math.random() * number);\n}\n</code></pre></div>\n<p>这也可以写成下面这样：</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>function randomNumber(number) {\n var result = Math.floor(Math.random() * number);\n return result;\n}\n</code></pre></div>\n<p>但是第一个版本写得更快，而且更紧凑。</p>\n<p>我们每次调用函数都返回<code>Math.floor(Math.random()*number)</code>计算的数学结果。这个返回值出现在调用函数的位置上，并且代码继续。例如，如果我们运行下面的行：</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>ctx.arc(random(WIDTH), random(HEIGHT), random(50), 0, 2 * Math.PI);\n</code></pre></div>\n<p>这三次<code>random()</code>调用分别返回值 500, 200 和 35，实际上这一行这样运行：</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>ctx.arc(500, 200, 35, 0, 2 * Math.PI);\n</code></pre></div>\n<p>在运行该行之前，首先运行该行上的函数调用，并用其返回值替换该函数调用。</p>"}},{"type":"prose","value":{"id":"主动学习：我们自己的返回值函数","title":"主动学习：我们自己的返回值函数","isH3":false,"content":"<p>让我们着手编写具有我们自己的返回值的函数。</p>\n<ol>\n<li>\n<p>首先，从 GitHub 的<a href=\"https://github.com/mdn/learning-area/blob/main/javascript/building-blocks/functions/function-library.html\" class=\"external\" target=\"_blank\">function-library.html</a>文件复制一份本地副本。这是一个简单的 HTML 页面包含一个 <a href=\"/zh-CN/docs/Web/HTML/Element/input\"><code><input></code></a> 文本域和一个段落。还有一个 <a href=\"/zh-CN/docs/Web/HTML/Element/script\"><code><script></code></a> 元素，我们在两个变量中存储了对两个 HTML 元素的引用。这个小页面允许你在文本框中输入一个数字，并在下面的段落中显示不同的数字。</p>\n</li>\n<li>\n<p>让我们添加一些有用的函数。在现有的两行 JavaScript 下面，添加以下函数定义：</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>function squared(num) {\n return num * num;\n}\n\nfunction cubed(num) {\n return num * num * num;\n}\n\nfunction factorial(num) {\n var x = num;\n while (x > 1) {\n num *= x - 1;\n x--;\n }\n return num;\n}\n</code></pre></div>\n<p><code>squared()</code> 和 <code>cubed()</code> 功能是相当明显的 - 他们的平方或立方的数作为一个参数返回。factorial() 函数返回给定数字的阶乘。</p>\n</li>\n<li>\n<p>接下来，我们将包括一种打印输入到文本输入中的数字的信息的方法。在现有函数下面输入以下事件处理程序：</p>\n<div class=\"code-example\"><div class=\"example-header\"><span class=\"language-name\">js</span></div><pre class=\"brush: js notranslate\"><code>input.onchange = function () {\n var num = input.value;\n if (isNaN(num)) {\n para.textContent = \"You need to enter a number!\";\n } else {\n para.textContent =\n num +\n \" squared is \" +\n squared(num) +\n \". \" +\n num +\n \" cubed is \" +\n cubed(num) +\n \". \" +\n num +\n \" factorial is \" +\n factorial(num) +\n \".\";\n }\n};\n</code></pre></div>\n<p>这里我们创建一个<code>onchange</code>事件处理程序，当文本框上面的 change 事件被触发的之后，事件处理程序就会运行 - 就是说，一个新的值被输入到文本框并且被提交（就比如，输入一个值，然后按 Tab）。当这个匿名函数运行时，输入框中的值将被存储在<code>num</code>变量中。</p>\n<p>接下来，我们进行条件测试——如果输入的值不是数字，则在段落中打印错误消息。if 语句判断<a href=\"/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/isNaN\">isNaN(num)</a>表达式是否返回 true。我们用<code>isNaN()</code>函数测试<code>num</code>的值是否不是一个数字 - 如果不是数字，就返回<code>true</code>，否则返回<code>false</code>。</p>\n<p>如果测试返回 false，则数值是一个数字，所以我们在段落元素中打印出一个句子，说明数字的平方、立方体和阶乘是什么。这句话叫 squared()，cubed()，和 factorial() 函数来获得所需的值。</p>\n</li>\n<li>\n<p>保存你的代码，将其加载到浏览器中，然后尝试。</p>\n</li>\n</ol>\n<div class=\"notecard note\">\n<p><strong>备注：</strong>\n如果你有麻烦让例子工作，对比<a href=\"https://github.com/mdn/learning-area/blob/main/javascript/building-blocks/functions/function-library-finished.html\" class=\"external\" target=\"_blank\">GitHub 的已完成版</a>检查你的代码（或<a href=\"https://mdn.github.io/learning-area/javascript/building-blocks/functions/function-library-finished.html\" class=\"external\" target=\"_blank\">看它在线运行</a>），或寻求我们的帮助。</p>\n</div>\n<p>在这一点上，我们希望你编写一个自己的几个函数，并将它们添加到库中。这个数的平方根或立方根，或一个圆的周长和半径是多少？</p>\n<p>这个练习提出了一些重要的观点，除了研究如何使用返回语句之外。此外，我们还有：</p>\n<ul>\n<li>查看另一个将错误处理写入函数的示例。它是否提供了任何必要的参数通常是一个好主意，另一方面对可选参数提供默认值。这样，你的程序就不太可能出错了。</li>\n<li>关于创建函数库思想的思考。随着你深入到你的编程生涯，你将开始一次又一次地做同样的事情。这是一个好主意，开始保持你自己的实用工具库，你经常使用 - 你可以把它们复制到你的新代码，甚至只是把它应用到任何你需要的 HTML 页面。</li>\n</ul>"}},{"type":"prose","value":{"id":"结论","title":"结论","isH3":false,"content":"<p>因此，我们让它 - 功能是有趣的，非常有用的，虽然有很多要谈论他们的语法和功能，相当容易理解的正确的文章学习。</p>\n<p>如果你有什么不明白的地方，可以再通读一遍，或者<a href=\"/zh-CN/docs/Learn_web_development#contact_us\">联系我们</a>寻求帮助。</p>"}},{"type":"prose","value":{"id":"参见","title":"参见","isH3":false,"content":"<ul>\n<li><a href=\"/zh-CN/docs/Web/JavaScript/Reference/Functions\">Functions in-depth</a> — 详细介绍更多高级功能相关信息的指南。</li>\n<li><a href=\"https://www.impressivewebs.com/callback-functions-javascript/\" class=\"external\" target=\"_blank\">Callback functions in JavaScript</a> — 一个常见的 JavaScript 模式是把一个函数传递给另一个函数作为参数，然后在第一个函数中调用它。这有点超出了这门课的范围，但值得学习很久。</li>\n</ul>\n<ul class=\"prev-next\"><li><a class=\"button secondary\" href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Build_your_own_function\"><span class=\"button-wrap\"> 上一页 </span></a></li><li><a class=\"button secondary\" href=\"/zh-CN/docs/Learn_web_development/Core/Scripting\"><span class=\"button-wrap\"> 概述：创建 JavaScript 代码块</span></a></li><li><a class=\"button secondary\" href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Events\"><span class=\"button-wrap\"> 下一页 </span></a></li></ul>"}}],"isActive":true,"isMarkdown":true,"isTranslated":true,"locale":"zh-CN","mdn_url":"/zh-CN/docs/Learn_web_development/Core/Scripting/Return_values","modified":"2024-12-25T01:16:37.000Z","native":"中文 (简体)","noIndexing":false,"other_translations":[{"locale":"en-US","title":"Function return values","native":"English (US)"},{"locale":"de","title":"Funktionsrückgabewerte","native":"Deutsch"},{"locale":"es","title":"Una función retorna valores","native":"Español"},{"locale":"fr","title":"Valeurs de retour des fonctions","native":"Français"},{"locale":"ja","title":"関数の返値","native":"日本語"},{"locale":"ko","title":"함수 반환 값","native":"한국어"},{"locale":"pt-BR","title":"Valores de retorno de função","native":"Português (do Brasil)"},{"locale":"ru","title":"Возвращаемые значения функций","native":"Русский"}],"pageTitle":"函数返回值 - 学习 Web 开发 | MDN","parents":[{"uri":"/zh-CN/docs/Learn_web_development","title":"学习 Web 开发"},{"uri":"/en-US/docs/Learn_web_development/Core","title":"Core learning modules"},{"uri":"/zh-CN/docs/Learn_web_development/Core/Scripting","title":"创建 JavaScript 代码块"},{"uri":"/zh-CN/docs/Learn_web_development/Core/Scripting/Return_values","title":"函数返回值"}],"popularity":null,"short_title":"函数返回值","sidebarHTML":"<ol><li class=\"section\"><a href=\"/zh-CN/docs/Learn_web_development/Getting_started\">入门模块</a></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Getting_started/Environment_setup\">配置环境</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Getting_started/Environment_setup/Installing_software\">安装基础软件</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Getting_started/Environment_setup/Browsing_the_web\">网页、网站、网络服务器和搜索引擎的区别是什么？</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Environment_setup/Code_editors\" class=\"only-in-en-us\">Code editors</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Getting_started/Environment_setup/Dealing_with_files\">处理文件</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Getting_started/Environment_setup/Command_line\">命令行速成课</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Getting_started/Your_first_website\">你的第一个网站</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Getting_started/Your_first_website/What_will_your_website_look_like\">你的网站会是什么样子？</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Getting_started/Your_first_website/Creating_the_content\">HTML 基础</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Getting_started/Your_first_website/Styling_the_content\">CSS 基础</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Getting_started/Your_first_website/Adding_interactivity\">JavaScript 基础</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Getting_started/Your_first_website/Publishing_your_website\">发布你的网站</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Getting_started/Web_standards\" class=\"only-in-en-us\">Web 标准</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Getting_started/Web_standards/How_the_web_works\">万维网是如何工作的</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Getting_started/Web_standards/The_web_standards_model\">Web 和 Web 标准</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Web_standards/How_browsers_load_websites\" class=\"only-in-en-us\">How browsers load websites</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/en-US/docs/Learn_web_development/Getting_started/Soft_skills\" class=\"only-in-en-us\">软性技能</a></summary><ol><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Soft_skills/Research_and_learning\" class=\"only-in-en-us\">Research and learning</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Soft_skills/Collaboration_and_teamwork\" class=\"only-in-en-us\">Collaboration and teamwork</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Soft_skills/Workflows_and_processes\" class=\"only-in-en-us\">Workflows and processes</a></li><li><a href=\"/en-US/docs/Learn_web_development/Getting_started/Soft_skills/Job_interviews\" class=\"only-in-en-us\">Succeeding in job interviews</a></li></ol></details></li><li class=\"section\"><a href=\"/en-US/docs/Learn_web_development/Core\" class=\"only-in-en-us\">核心模块</a></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content\">使用 HTML 构建内容</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/Basic_HTML_syntax\">开始学习 HTML</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/Webpage_metadata\">“头”里有什么——HTML 元信息</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/Headings_and_paragraphs\">HTML 文本处理基础</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/Emphasis_and_importance\">强调与重要性</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/Lists\" class=\"only-in-en-us\">Lists</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/Structuring_documents\">文档与网站架构</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/Advanced_text_features\">文本格式进阶</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/Creating_links\">创建超链接</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/Marking_up_a_letter\">标记信件</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/Structuring_a_page_of_content\">构建网页内容</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/HTML_images\">HTML 中的图片</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/HTML_video_and_audio\">视频和音频内容</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/Mozilla_splash_page\">Mozilla 欢迎页面</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/HTML_table_basics\">HTML 表格基础</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/Table_accessibility\">HTML 表格进阶特性和无障碍</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/Planet_data_table\">作业：构建行星数据</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Structuring_content/HTML_forms\" class=\"only-in-en-us\">Forms and buttons in HTML</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Structuring_content/Debugging_HTML\">HTML 调试</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics\">CSS 样式基础</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/What_is_CSS\">CSS 如何运行</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Getting_started\">让我们开始 CSS 的学习之旅</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Styling_a_bio_page\">运用你的新知识</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Basic_selectors\">CSS 选择器</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Attribute_selectors\">属性选择器</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Pseudo_classes_and_elements\">伪类和伪元素</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Combinators\">关系选择器</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Box_model\">盒模型</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Handling_conflicts\">层叠、优先级与继承</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Values_and_units\">CSS 值和单位</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Sizing\">在 CSS 中调整大小</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Backgrounds_and_borders\">背景与边框</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Overflow\">溢出的内容</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Images_media_forms\">图像、媒体和表单元素</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Tables\">样式化表格</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Debugging_CSS\">调试 CSS</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Fundamental_CSS_comprehension\">基本的 CSS 理解</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Fancy_letterheaded_paper\">创建精美的信纸</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Styling_basics/Cool-looking_box\">一个漂亮的盒子</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Core/Text_styling\">CSS 文本样式</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Text_styling/Fundamentals\">基本文本和字体样式</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Text_styling/Styling_lists\">为列表添加样式</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Text_styling/Styling_links\">样式化链接</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Text_styling/Web_fonts\">Web 字体</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Text_styling/Typesetting_a_homepage\">作业：排版社区大学首页</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Core/CSS_layout\">CSS 排版</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Core/CSS_layout/Introduction\">介绍 CSS 布局</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/CSS_layout/Floats\">浮动</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/CSS_layout/Positioning\">定位</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/CSS_layout/Flexbox\">弹性盒子</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/CSS_layout/Grids\">网格</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/CSS_layout/Responsive_Design\">响应式设计</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/CSS_layout/Media_queries\">媒体查询入门指南</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/CSS_layout/Fundamental_Layout_Comprehension\">作业：基本布局理解</a></li></ol></details></li><li class=\"toggle\"><details open=\"\"><summary><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting\">使用 JavaScript 动态编码</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/What_is_JavaScript\">什么是 JavaScript？</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/A_first_splash\">JavaScript 初体验</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/What_went_wrong\">查找并解决 JavaScript 代码的错误</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Variables\">如何存储你需要的信息——变量</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Math\">JavaScript 中的基础数学 — 数字和操作符</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Strings\">文本处理——JavaScript 中的字符串</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Useful_string_methods\">有用的字符串方法</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Arrays\">数组</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Silly_story_generator\">笑话生成器</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Conditionals\">在代码中做决定——条件语句</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Loops\">循环吧，代码</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Functions\">函数——可复用的代码块</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Build_your_own_function\">创建你自己的函数</a></li><li><em><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Return_values\" aria-current=\"page\">函数返回值</a></em></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Events\">事件介绍</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Event_bubbling\">事件冒泡</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Image_gallery\">图片库</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Object_basics\">JavaScript 对象基础</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/DOM_scripting\">DOM 脚本简介</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Network_requests\">从服务器获取数据</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/JSON\">使用 JSON</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Scripting/Debugging_JavaScript\">处理常见的 JavaScript 问题</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Core/Frameworks_libraries\">JavaScript 架构和库</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Frameworks_libraries/Introduction\">客户端框架介绍</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Frameworks_libraries/Main_features\">框架的主要特性</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Frameworks_libraries/React_getting_started\">React 入门</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Frameworks_libraries/React_todo_list_beginning\">开始我们的 React 待办清单</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Frameworks_libraries/React_components\">组件化我们的 React App</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_interactivity_events_state\" class=\"only-in-en-us\">React interactivity: Events and state</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_interactivity_filtering_conditional_rendering\" class=\"only-in-en-us\">React interactivity: Editing, filtering, conditional rendering</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_accessibility\" class=\"only-in-en-us\">Accessibility in React</a></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Frameworks_libraries/React_resources\" class=\"only-in-en-us\">React resources</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Core/Accessibility\">无障碍</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Accessibility/What_is_accessibility\">什么是无障碍？</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Accessibility/Tooling\">解决常见的无障碍问题</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Accessibility/HTML\">HTML：无障碍的良好基础</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Accessibility/CSS_and_JavaScript\">CSS 和 JavaScript 无障碍最佳实践</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Accessibility/WAI-ARIA_basics\">WAI-ARIA 基础</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Accessibility/Multimedia\">多媒体无障碍</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Accessibility/Mobile\">移动端无障碍</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Accessibility/Accessibility_troubleshooting\">测验：无障碍疑难解答</a></li></ol></details></li><li><a href=\"/en-US/docs/Learn_web_development/Core/Design_for_developers\" class=\"only-in-en-us\">为开发人员设计</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Core/Version_control\">版本控制</a></li><li class=\"section\"><a href=\"/en-US/docs/Learn_web_development/Extensions\" class=\"only-in-en-us\">扩展模块</a></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects\">Advanced JavaScript objects</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Object_prototypes\">对象原型</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Object-oriented_programming\">面向对象编程基本概念</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Classes_in_JavaScript\">JavaScript 中的类</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Object_building_practice\">实践对象构造</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Advanced_JavaScript_objects/Adding_bouncing_balls_features\">为“弹球”示例添加新功能</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Client-side_APIs\">客户端 Web API</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Client-side_APIs/Introduction\">Web API 简介</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Client-side_APIs/Video_and_audio_APIs\">视频和音频 API</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Client-side_APIs/Drawing_graphics\">绘图</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Client-side_APIs/Client-side_storage\">客户端存储</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Client-side_APIs/Third_party_APIs\">第三方 API</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Async_JS\">异步 JavaScript</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Async_JS/Introducing\">异步 JavaScript 简介</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Async_JS/Promises\">如何使用 Promise</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Async_JS/Implementing_a_promise-based_API\">如何实现基于 Promise 的 API</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Async_JS/Introducing_workers\">worker 简介</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Async_JS/Sequencing_animations\">序列动画</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Forms\">Web 表单</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Forms/Your_first_form\">创建我的第一个表单</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Forms/How_to_structure_a_web_form\">如何构建 HTML 表单</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Forms/Basic_native_form_controls\">原生表单部件</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Forms/HTML5_input_types\">HTML5 的输入（input）类型</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Forms/Other_form_controls\">其他表单控件</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Forms/Styling_web_forms\">样式化 Web 表单</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Forms/Advanced_form_styling\">表单样式化进阶</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Forms/UI_pseudo-classes\">UI 伪类</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Forms/Form_validation\">表单数据校验</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Forms/Sending_and_retrieving_form_data\">发送表单数据</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Client-side_tools\">理解客户端工具</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Client-side_tools/Overview\">客户端工具概述</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Client-side_tools/Package_management\">软件包管理基础</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Client-side_tools/Introducing_complete_toolchain\">介绍完整的工具链</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Client-side_tools/Deployment\">部署我们的应用</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side\">服务端网站</a></summary><ol><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/First_steps\">服务端基础</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/First_steps/Introduction\">服务端编程介绍</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/First_steps/Client-Server_overview\">客户端服务端交互概述</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/First_steps/Web_frameworks\">服务端 web 框架</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/First_steps/Website_security\">站点安全</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django\">Django web 框架（Python）</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/Introduction\">Django 介绍</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/development_environment\">设置 Django 开发环境</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/Tutorial_local_library_website\">Django Tutorial: The Local Library website</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/skeleton_website\">Django Tutorial Part 2: 创建网站的地基</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/Models\">Django Tutorial Part 3: 使用模型</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/Admin_site\">Django Tutorial Part 4: Django 管理员站点</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/Home_page\">Django 教程 5：主页构建</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/Generic_views\">Django 教程 6: 通用列表和详细信息视图</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/Sessions\">Django 教程 7: 会话框架</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/Authentication\">Django 教程 8：用户授权与许可</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/Forms\">Django 教程 9: 使用表单</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/Testing\">Django 教程 10: 测试 Django 网页应用</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/Deployment\">Django 教程 11：部署 Django 到生产环境</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/web_application_security\">Django Web 应用安全</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Django/django_assessment_blog\">评估：DIY Django 微博客</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs\">Express web 框架（Node.js）</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Introduction\">Express/Node 入门</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/development_environment\">设置 Node 开发环境</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Tutorial_local_library_website\">Express 教程：本地图书馆网站</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/skeleton_website\">Express 教程 2：创建站点框架</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/mongoose\">Express 教程 3：使用数据库 (Mongoose)</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/routes\">Express 教程 4：路由和控制器</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/Displaying_data\">Express 教程 5: 呈现图书馆数据</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/forms\">Express 教程 6: 使用表单</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Server-side/Express_Nodejs/deployment\">Express 教程 7：部署到生产环境</a></li></ol></details></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Performance\">Web 性能</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Performance/why_web_performance\">Web 性能的重要性</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Performance/What_is_web_performance\">什么是 web 性能？</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Performance/Perceived_performance\">感知性能</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Performance/Measuring_performance\">测量性能</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Performance/Multimedia\">多媒体：图片</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Performance/video\">多媒体：视频</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Performance/JavaScript\">JavaScript 性能优化</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Performance/HTML\">HTML 性能优化</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Performance/CSS\">CSS 性能优化</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Performance/business_case_for_performance\">web 性能的商业案例</a></li></ol></details></li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Testing\">测试</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Testing/Introduction\">跨浏览器测试介绍</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Testing/Testing_strategies\">测试的策略</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Testing/HTML_and_CSS\">处理常见的 HTML 和 CSS 问题</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Testing/Feature_detection\">实现特性检测</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Testing/Automated_testing\">自动化测试简介</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Extensions/Testing/Your_own_automation_environment\">搭建自己的自动化测试环境</a></li></ol></details></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Transform_animate\" class=\"only-in-en-us\">CSS 变换与动画化</a></li><li><a href=\"/en-US/docs/Learn_web_development/Extensions/Security_privacy\" class=\"only-in-en-us\">安全与隐私</a></li><li class=\"section\">更多资源</li><li class=\"toggle\"><details><summary><a href=\"/zh-CN/docs/Learn_web_development/Howto\">如何解决常见问题</a></summary><ol><li><a href=\"/zh-CN/docs/Learn_web_development/Howto/Solve_HTML_problems\">使用 HTML 解决常见问题</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Howto/Solve_CSS_problems\">解决常见的 CSS 问题</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Howto/Solve_JavaScript_problems\">解决 JavaSctript 代码的常见问题</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Howto/Web_mechanics\">Web 机制</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Howto/Tools_and_setup\">工具和安装</a></li><li><a href=\"/zh-CN/docs/Learn_web_development/Howto/Design_and_accessibility\">设计与无障碍</a></li></ol></details></li><li><a href=\"/en-US/docs/Learn_web_development/About\" class=\"only-in-en-us\">关于</a></li><li><a href=\"/en-US/docs/Learn_web_development/Educators\" class=\"only-in-en-us\">面向教育工作者的资源</a></li><li><a href=\"/en-US/docs/Learn_web_development/Changelog\" class=\"only-in-en-us\">更新日志</a></li></ol>","source":{"folder":"zh-cn/learn_web_development/core/scripting/return_values","github_url":"https://github.com/mdn/translated-content/blob/main/files/zh-cn/learn_web_development/core/scripting/return_values/index.md","last_commit_url":"https://github.com/mdn/translated-content/commit/b61971bb4836b5fda657fac82930c2c32017a3f0","filename":"index.md"},"summary":"函数返回值 - 是本章中最后一个基础概念，让我们一起来瞧瞧.。有些函数在执行完毕后不会返回一个有用的值，但有些会，重要的是理解返回的是什么，怎样使用这些值在你的代码中，我们将在下面讨论这些。","title":"函数返回值","toc":[{"text":"什么是返回值？","id":"什么是返回值？"},{"text":"主动学习：我们自己的返回值函数","id":"主动学习：我们自己的返回值函数"},{"text":"结论","id":"结论"},{"text":"参见","id":"参见"}],"pageType":"learn-module-chapter"}}</script></body></html>