72 lines
2.4 KiB
Markdown
72 lines
2.4 KiB
Markdown
---
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id: 587d7b86367417b2b2512b3c
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title: Use Caution When Reinitializing Variables Inside a Loop
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challengeType: 1
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videoUrl: ''
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localeTitle: 在循环内重新初始化变量时请小心
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---
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## Description
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<section id="description">有时需要在循环中保存信息，增加计数器或重置变量。一个潜在的问题是变量要么重新初始化，要么不重新初始化，反之亦然。如果您不小心重置了用于终端条件的变量，导致无限循环，这将特别危险。使用<code>console.log()</code>在循环的每个循环中打印变量值可以发现与重置相关的错误行为，或者无法重置变量。 </section>
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## Instructions
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<section id="instructions">以下函数应该创建一个具有<code>m</code>行和<code>n</code>列零的二维数组。不幸的是，它没有产生预期的输出，因为<code>row</code>变量没有在外部循环中重新初始化（设置回空数组）。修复代码，使其返回正确的3x2零数组，看起来像<code>[[0, 0], [0, 0], [0, 0]]</code> 。 </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: 您的代码应该将<code>matrix</code>变量设置为一个数组，每个数组包含3行，每列2列零。
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testString: 'assert(JSON.stringify(matrix) == "[[0,0],[0,0],[0,0]]", "Your code should set the <code>matrix</code> variable to an array holding 3 rows of 2 columns of zeroes each.");'
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- text: <code>matrix</code>变量应该有3行。
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testString: 'assert(matrix.length == 3, "The <code>matrix</code> variable should have 3 rows.");'
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- text: <code>matrix</code>变量每行应有2列。
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testString: 'assert(matrix[0].length == 2 && matrix[1].length === 2 && matrix[2].length === 2, "The <code>matrix</code> variable should have 2 columns in each row.");'
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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 zeroArray(m, n) {
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// Creates a 2-D array with m rows and n columns of zeroes
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let newArray = [];
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let row = [];
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for (let i = 0; i < m; i++) {
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// Adds the m-th row into newArray
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for (let j = 0; j < n; j++) {
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// Pushes n zeroes into the current row to create the columns
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row.push(0);
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}
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// Pushes the current row, which now has n zeroes in it, to the array
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newArray.push(row);
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}
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return newArray;
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}
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let matrix = zeroArray(3, 2);
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console.log(matrix);
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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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