65 lines
2.4 KiB
Markdown
65 lines
2.4 KiB
Markdown
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---
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id: 587d7b88367417b2b2512b47
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title: Use the Rest Operator with Function Parameters
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challengeType: 1
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videoUrl: ''
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localeTitle: 将Rest运算符与函数参数一起使用
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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引入了函数参数的<dfn>rest运算符</dfn> 。使用rest运算符，您可以创建带有可变数量参数的函数。这些参数存储在一个数组中，以后可以从函数内部访问。看看这段代码： <blockquote> function howMany（... args）{ <br>返回“你已经通过”+ args.length +“arguments。”; <br> } <br> console.log（howMany（0,1,2））; //你已经传递了3个参数<br> console.log（howMany（“string”，null，[1,2,3]，{}））; //你已经传递了4个参数。 </blockquote>其余运算符无需检查<code>args</code>数组，并允许我们在<code>args</code>数组上应用<code>map()</code> ， <code>filter()</code>和<code>reduce()</code> 。 </section>
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## Instructions
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<section id="instructions">修改函数<code>sum</code> ，使其使用rest运算符，并以相同的方式使用任意数量的参数。 </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>sum(0,1,2)</code>的结果应为3'
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testString: 'assert(sum(0,1,2) === 3, "The result of <code>sum(0,1,2)</code> should be 3");'
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- text: '<code>sum(1,2,3,4)</code>的结果应为10'
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testString: 'assert(sum(1,2,3,4) === 10, "The result of <code>sum(1,2,3,4)</code> should be 10");'
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- text: <code>sum(5)</code>的结果应为5
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testString: 'assert(sum(5) === 5, "The result of <code>sum(5)</code> should be 5");'
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- text: <code>sum()</code>的结果应为0
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testString: 'assert(sum() === 0, "The result of <code>sum()</code> should be 0");'
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- text: <code>sum</code>函数在<code>args</code>参数上使用<code>...</code> spread运算符。
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testString: 'getUserInput => assert(getUserInput("index").match(/function\s+sum\s*\(\s*...args\s*\)\s*{/g), "The <code>sum</code> function uses the <code>...</code> spread operator on the <code>args</code> parameter.");'
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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 sum = (function() {
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"use strict";
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return function sum(x, y, z) {
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const args = [ x, y, z ];
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return args.reduce((a, b) => a + b, 0);
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};
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})();
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console.log(sum(1, 2, 3)); // 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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