JavaScript 中的二维数组
本教程介绍了如何在 JavaScript 中声明一个二维数组。在二维数组中,元素以行和列的形式组织成矩阵。它就像一个数组,其元素是一维数组。
我们使用数组构造函数创建给定长度的空数组。然后,我们可以使用 for
循环为每个元素创建一个数组。
const m = 4;
const n = 5;
let arr = new Array(m);
for (var i = 0; i < m; i++) {
arr[i] = new Array(n);
}
console.log(arr);
输出:
Array [ [ null, null, null, null, null ], [ null, null, null, null, null ], [ null, null, null, null, null ], [ null, null, null, null, null ] ]
我们可以使用 JavaScript 中的文字符号方法来创建二维数组。
const m = 4;
const n = 5;
let arr = [];
for (var i = 0; i < m; i++) {
arr[i] = [];
}
console.log(arr);
输出:
Array [ [], [], [], [] ]
Array.from()
方法从任何 JavaScript 对象返回一个数组对象。
const m = 4;
const n = 5;
let arr = Array.from(Array(m), () => new Array(n));
console.log(arr);
输出:
Array [ [ null, null, null, null, null ], [ null, null, null, null, null ], [ null, null, null, null, null ], [ null, null, null, null, null ] ]
Array.map()
方法还通过将数组元素映射到空数组来帮助创建 2D 数组。
const m = 4;
const n = 5;
let arr = Array(m).fill().map(() => Array(n));
console.log(arr);
输出:
Array [ [ null, null, null, null, null ], [ null, null, null, null, null ], [ null, null, null, null, null ], [ null, null, null, null, null ] ]
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