51 lines
1.1 KiB
Markdown
51 lines
1.1 KiB
Markdown
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---
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title: Use Caution When Reinitializing Variables Inside a Loop
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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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## 在循环内重新初始化变量时请小心
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* 必须通过重新定义`row[]`的范围来解决这一挑战。
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* 以下是所需矩阵的示例。
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```javascript
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[
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[0][0],
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[0][0],
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[0][0]
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]
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```
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* 然而，当前的矩阵 - 见下文 - 远离所需的矩阵
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```javascript
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[
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[0][0][0][0][0][0],
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[0][0][0][0][0][0],
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[0][0][0][0][0][0]
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]
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```
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* 由于`row[]`数组被声明为嵌套for循环之外的全局变量，因此发生此错误。
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* 但是，要正确填充矩阵，必须在每次外部循环迭代后重置`row[]`数组。
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## 解
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```javascript
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function zeroArray(m, n) {
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let newArray = [];
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for (let i = 0; i < m; i++) {
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let row = []; /* <----- row has been declared inside the outer loop.
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Now a new row will be initialised during each iteration of the outer loop allowing
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for the desired matrix. */
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for (let j = 0; j < n; j++) {
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row.push(0);
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}
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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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