66 lines
2.6 KiB
Markdown
66 lines
2.6 KiB
Markdown
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---
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id: 587d7da9367417b2b2512b67
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title: Add Elements to the End of an Array Using concat Instead of push
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challengeType: 1
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videoUrl: ''
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localeTitle: 使用concat将元素添加到数组的末尾而不是push
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---
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## Description
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<section id="description">函数式编程就是创建和使用非变异函数。最后一个挑战是将<code>concat</code>方法作为一种将数组组合成新数组而不改变原始数组的方法。将<code>concat</code>与<code>push</code>方法进行比较。 <code>Push</code>将一个项添加到调用它的同一个数组的末尾，这会改变该数组。这是一个例子： <blockquote> var arr = [1,2,3]; <br> arr.push（[4,5,6]）; <br> // arr更改为[1,2,3，[4,5,6]] <br> //不是函数式编程方式</blockquote> <code>Concat</code>提供了一种在数组末尾添加新项目而无任何变异副作用的方法。 </section>
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## Instructions
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<section id="instructions">更改<code>nonMutatingPush</code>函数，使其使用<code>concat</code>将<code>newItem</code>添加到<code>original</code>结尾而不是<code>push</code> 。该函数应返回一个数组。 </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: 您的代码应使用<code>concat</code>方法。
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testString: 'assert(code.match(/\.concat/g), "Your code should use the <code>concat</code> method.");'
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- text: 您的代码不应使用<code>push</code>方法。
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testString: 'assert(!code.match(/\.push/g), "Your code should not use the <code>push</code> method.");'
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- text: 第<code>first</code>数组不应该改变。
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testString: 'assert(JSON.stringify(first) === JSON.stringify([1, 2, 3]), "The <code>first</code> array should not change.");'
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- text: <code>second</code>数组不应该改变。
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testString: 'assert(JSON.stringify(second) === JSON.stringify([4, 5]), "The <code>second</code> array should not change.");'
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- text: '<code>nonMutatingPush([1, 2, 3], [4, 5])</code>应该返回<code>[1, 2, 3, 4, 5]</code> 。'
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testString: 'assert(JSON.stringify(nonMutatingPush([1, 2, 3], [4, 5])) === JSON.stringify([1, 2, 3, 4, 5]), "<code>nonMutatingPush([1, 2, 3], [4, 5])</code> should return <code>[1, 2, 3, 4, 5]</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 nonMutatingPush(original, newItem) {
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// Add your code below this line
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return original.push(newItem);
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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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nonMutatingPush(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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// solution required
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```
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</section>
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