70 lines
3.5 KiB
Markdown
70 lines
3.5 KiB
Markdown
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---
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id: 587d7b7b367417b2b2512b13
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title: Copy an Array with the Spread Operator
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challengeType: 1
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videoUrl: ''
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localeTitle: 使用Spread Operator复制数组
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---
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## Description
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<section id="description">虽然<code>slice()</code>允许我们选择要复制的数组元素，但在其他几个有用的任务中，ES6的新<dfn>扩展运算符</dfn>允许我们使用简单且高度可读的语法轻松地按顺序复制<em>所有</em>数组的元素。扩展语法看起来像这样： <code>...</code>在实践中，我们可以使用spread运算符来复制数组，如下所示： <blockquote> let thisArray = [true，true，undefined，false，null]; <br>让thatArray = [... thisArray]; <br> // thatArray等于[true，true，undefined，false，null] <br> // thisArray保持不变，与thatArray相同</blockquote></section>
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## Instructions
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<section id="instructions">我们定义了一个函数<code>copyMachine</code> ，它将<code>arr</code> （数组）和<code>num</code> （数字）作为参数。该函数应该返回一个由<code>arr</code>的<code>num</code>副本组成的新数组。我们为您完成了大部分工作，但它还没有正常工作。使用扩展语法修改函数以使其正常工作（提示：我们已经介绍过的另一种方法可能会派上用场！）。 </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>copyMachine([true, false, true], 2)</code>应返回<code>[[true, false, true], [true, false, true]]</code>'
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testString: 'assert.deepEqual(copyMachine([true, false, true], 2), [[true, false, true], [true, false, true]], "<code>copyMachine([true, false, true], 2)</code> should return <code>[[true, false, true], [true, false, true]]</code>");'
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- text: '<code>copyMachine([1, 2, 3], 5)</code>应返回<code>[[1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3]]</code>'
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testString: 'assert.deepEqual(copyMachine([1, 2, 3], 5), [[1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3]], "<code>copyMachine([1, 2, 3], 5)</code> should return <code>[[1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3], [1, 2, 3]]</code>");'
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- text: '<code>copyMachine([true, true, null], 1)</code>应该返回<code>[[true, true, null]]</code>'
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testString: 'assert.deepEqual(copyMachine([true, true, null], 1), [[true, true, null]], "<code>copyMachine([true, true, null], 1)</code> should return <code>[[true, true, null]]</code>");'
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- text: '<code>copyMachine(["it works"], 3)</code>应该返回<code>[["it works"], ["it works"], ["it works"]]</code>'
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testString: 'assert.deepEqual(copyMachine(["it works"], 3), [["it works"], ["it works"], ["it works"]], "<code>copyMachine(["it works"], 3)</code> should return <code>[["it works"], ["it works"], ["it works"]]</code>");'
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- text: <code>copyMachine</code>函数应该使用带有数组<code>arr</code>的<code>spread operator</code>
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testString: 'assert.notStrictEqual(copyMachine.toString().indexOf(".concat(_toConsumableArray(arr))"), -1, "The <code>copyMachine</code> function should utilize the <code>spread operator</code> with array <code>arr</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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function copyMachine(arr, num) {
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let newArr = [];
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while (num >= 1) {
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// change code below this line
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// change code above this line
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num--;
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}
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return newArr;
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}
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// change code here to test different cases:
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console.log(copyMachine([true, false, true], 2));
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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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