81 lines
2.1 KiB
Markdown
81 lines
2.1 KiB
Markdown
---
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id: 587d7da9367417b2b2512b66
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title: Combine Two Arrays Using the concat Method
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challengeType: 1
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forumTopicId: 301229
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localeTitle: 使用 concat 方法组合两个数组
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---
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## Description
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<section id='description'>
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<code>Concatenation</code>意思是将元素连接到尾部。同理，JavaScript 为字符串和数组提供了<code>concat</code>方法。对数组来说，在一个数组上调用<code>concat</code>方法，然后提供另一个数组作为参数添加到第一个数组末尾，返回一个新数组，不会改变任何一个原始数组。举个例子：
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```js
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[1, 2, 3].concat([4, 5, 6]);
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// 返回新数组 [1, 2, 3, 4, 5, 6]
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```
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</section>
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## Instructions
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<section id='instructions'>
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在<code>nonMutatingConcat</code>函数里使用<code>concat</code>，将<code>attach</code>拼接到<code>original</code>尾部，返回拼接后的数组。
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</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: 应该使用<code>concat</code>方法。
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testString: assert(code.match(/\.concat/g));
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- text: 不能改变<code>first</code>数组。
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testString: assert(JSON.stringify(first) === JSON.stringify([1, 2, 3]));
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- text: 不能改变<code>second</code>数组。
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testString: assert(JSON.stringify(second) === JSON.stringify([4, 5]));
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- text: <code>nonMutatingConcat([1, 2, 3], [4, 5])</code>应返回<code>[1, 2, 3, 4, 5]</code>。
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testString: assert(JSON.stringify(nonMutatingConcat([1, 2, 3], [4, 5])) === JSON.stringify([1, 2, 3, 4, 5]));
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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 nonMutatingConcat(original, attach) {
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// Add your code below this line
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// Add your code above this line
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}
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var first = [1, 2, 3];
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var second = [4, 5];
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nonMutatingConcat(first, second);
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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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function nonMutatingConcat(original, attach) {
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// Add your code below this line
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return original.concat(attach);
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// Add your code above this line
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}
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var first = [1, 2, 3];
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var second = [4, 5];
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nonMutatingConcat(first, second);
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```
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</section>
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