67 lines
4.2 KiB
Markdown
67 lines
4.2 KiB
Markdown
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---
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id: 587d7b7b367417b2b2512b15
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title: Iterate Through All an Array's Items Using For Loops
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challengeType: 1
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videoUrl: ''
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localeTitle: 使用for循环遍历所有数组的项目
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---
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## Description
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<section id="description">有时在使用数组时，能够遍历每个项目以查找我们可能需要的一个或多个元素，或者根据哪些数据项符合某组标准来操作数组非常方便。 JavaScript提供了几种内置方法，每种方法都以稍微不同的方式迭代数组以实现不同的结果（例如<code>every()</code> ， <code>forEach()</code> ， <code>map()</code>等），但是这种技术最灵活并且为我们提供了最大的控制量是一个简单的<code>for</code>循环。考虑以下： <blockquote> function greaterThanTen（arr）{ <br>让newArr = []; <br> for（let i = 0; i <arr.length; i ++）{ <br> if（arr [i]> 10）{ <br> （ARR [I]）newArr.push; <br> } <br> } <br>返回newArr; <br> } <br><br> greaterThanTen（[2,12,8,14,80,0,1]）; <br> //返回[12,14,80] </blockquote>使用<code>for</code>循环，此函数遍历并访问数组的每个元素，并使其经受我们创建的简单测试。通过这种方式，我们可以轻松地以编程方式确定哪些数据项大于<code>10</code> ，并返回包含这些项的新数组。 </section>
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## Instructions
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<section id="instructions">我们定义了一个函数<code>filteredArray</code> ，它接受<code>arr</code> ，一个嵌套数组和<code>elem</code>作为参数，并返回一个新数组。 <code>elem</code>表示在<code>arr</code>嵌套的一个或多个数组上可能存在或不存在的元素。使用<code>for</code>循环修改函数，以返回已传递数组的过滤版本，以便删除嵌套在包含<code>elem</code> <code>arr</code>中的任何数组。 </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: '<code>filteredArray([[10, 8, 3], [14, 6, 23], [3, 18, 6]], 18)</code>应该返回<code>[ [10, 8, 3], [14, 6, 23] ]</code>'
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testString: 'assert.deepEqual(filteredArray([ [10, 8, 3], [14, 6, 23], [3, 18, 6] ], 18), [[10, 8, 3], [14, 6, 23]], "<code>filteredArray([[10, 8, 3], [14, 6, 23], [3, 18, 6]], 18)</code> should return <code>[ [10, 8, 3], [14, 6, 23] ]</code>");'
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- text: '<code>filteredArray([ ["trumpets", 2], ["flutes", 4], ["saxophones", 2] ], 2)</code>应返回<code>[ ["flutes", 4] ]</code>'
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testString: 'assert.deepEqual(filteredArray([ ["trumpets", 2], ["flutes", 4], ["saxophones", 2] ], 2), [["flutes", 4]], "<code>filteredArray([ ["trumpets", 2], ["flutes", 4], ["saxophones", 2] ], 2)</code> should return <code>[ ["flutes", 4] ]</code>");'
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- text: '<code>filteredArray([ ["amy", "beth", "sam"], ["dave", "sean", "peter"] ], "peter")</code>应该返回<code>[ ["amy", "beth", "sam"] ]</code>'
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testString: 'assert.deepEqual(filteredArray([["amy", "beth", "sam"], ["dave", "sean", "peter"]], "peter"), [["amy", "beth", "sam"]], "<code>filteredArray([ ["amy", "beth", "sam"], ["dave", "sean", "peter"] ], "peter")</code> should return <code>[ ["amy", "beth", "sam"] ]</code>");'
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- text: '<code>filteredArray([[3, 2, 3], [1, 6, 3], [3, 13, 26], [19, 3, 9]], 3)</code>应该返回<code>[ ]</code>'
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testString: 'assert.deepEqual(filteredArray([[3, 2, 3], [1, 6, 3], [3, 13, 26], [19, 3, 9]], 3), [], "<code>filteredArray([[3, 2, 3], [1, 6, 3], [3, 13, 26], [19, 3, 9]], 3)</code> should return <code>[ ]</code>");'
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- text: <code>filteredArray</code>函数应该使用<code>for</code>循环
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testString: 'assert.notStrictEqual(filteredArray.toString().search(/for/), -1, "The <code>filteredArray</code> function should utilize a <code>for</code> loop");'
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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 filteredArray(arr, elem) {
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let newArr = [];
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// change code below this line
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// change code above this line
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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(filteredArray([[3, 2, 3], [1, 6, 3], [3, 13, 26], [19, 3, 9]], 3));
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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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