61 lines
2.0 KiB
Markdown
61 lines
2.0 KiB
Markdown
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---
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id: 587d7b88367417b2b2512b46
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title: Set Default Parameters for Your Functions
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challengeType: 1
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videoUrl: ''
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localeTitle: 设置函数的默认参数
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---
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## Description
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<section id="description">为了帮助我们创建更灵活的函数，ES6引入了函数的<dfn>默认参数</dfn> 。看看这段代码： <blockquote> function greeting（name =“Anonymous”）{ <br>返回“你好”+名字; <br> } <br>的console.log（问候语（ “约翰”））; // 你好约翰<br>的console.log（问候（））; //你好匿名</blockquote>默认参数在未指定参数时启动（未定义）。正如您在上面的示例中所看到的，当您未为参数提供值时，参数<code>name</code>将接收其默认值<code>"Anonymous"</code> 。您可以根据需要为任意数量的参数添加默认值。 </section>
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## Instructions
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<section id="instructions">修改函数<code>increment</code>加入默认参数，这样它会加1 <code>number</code> ，如果<code>value</code>未指定。 </section>
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## Tests
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<section id='tests'>
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```yml
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tests:
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- text: '<code>increment(5, 2)</code>应为<code>7</code> 。'
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testString: 'assert(increment(5, 2) === 7, "The result of <code>increment(5, 2)</code> should be <code>7</code>.");'
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- text: <code>increment(5)</code>的结果应为<code>6</code> 。
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testString: 'assert(increment(5) === 6, "The result of <code>increment(5)</code> should be <code>6</code>.");'
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- text: 默认参数<code>1</code>用于<code>value</code> 。
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testString: 'getUserInput => assert(getUserInput("index").match(/value\s*=\s*1/g), "default parameter <code>1</code> was used for <code>value</code>.");'
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```
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</section>
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## Challenge Seed
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<section id='challengeSeed'>
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<div id='js-seed'>
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```js
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const increment = (function() {
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"use strict";
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return function increment(number, value) {
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return number + value;
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};
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})();
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console.log(increment(5, 2)); // returns 7
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console.log(increment(5)); // returns 6
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```
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</div>
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</section>
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## Solution
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<section id='solution'>
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```js
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// solution required
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```
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</section>
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