Does JavaScript have two-dimensional arrays?

JavaScript does not have two-dimensional arrays. There is no concept of a two-dimensional array in JavaScript, but you can set the value of an array element equal to an array, so that you can simulate the structure of a two-dimensional array; if the value of each element in a three-dimensional array is also an array, you can simulate a three-dimensional array. By analogy, multi-dimensional arrays can be defined through array nesting.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

JavaScript does not directly support two-dimensional arrays, but you can set the value of the array element equal to the array, so that the structure of the two-dimensional array can be simulated. If the value of each element in a three-dimensional array is also an array, a three-dimensional array can be simulated. By analogy, a multi-dimensional array can be defined through array nesting.

Example 1

The following defines a two-dimensional array.

var a = [  //定义二维数组
    [1.1, 1.2],
    [2.1, 2.2]
];

Example 2

The following example uses nested for statements to store positive numbers from 1 to 100 in the form of a two-dimensional array to design a two-dimensional array.

var a = [];
for (var i = 0; i < 10; i ++) {  //行循环
    var b = [];  //辅助数组
    for (var j = 0; j < 10; j ++) {  //列循环
        b[j] = i * 10 + j + 1;  //定义数组b的元素值
    }
    a[i] = b;  //把数组b赋值给数组a
}
console.log(a);  //返回1~100的二维数列

The sequence format is as follows:

a = [
    [1,2,3,4,5,6,7,8,9,10],
    [11,12,13,14,15,16,17,18,19,20],
    [21,22,23,24,25,26,27,28,29,30],
    [31,32,33,34,35,36,37,38,39,40],
    [41,42,43,44,45,46,47,48,49,50],
    [51,52,53,54,55,56,57,58,59,60],
    [61,62,63,64,65,66,67,68,69,70],
    [71,72,73,74,75,76,77,78,79,80],
    [81,82,83,84,85,86,87,88,89,90],
    [91,92,93,94,95,96,97,98,99,100]
];

Example 3

JavaScript does not support two-dimensional arrays, users can imitate the syntax format of two-dimensional arrays to define array. Although the following writing method is not grammatically compliant, JavaScript will not throw an exception.

var a = [];
a[0,0] = 1;
a[0,1] = 2;
a[1,0] = 3;
a[1,1] = 4;

If the length attribute is called, the return value is 2, indicating that there are only two elements, and the values ​​of the elements are read separately.

console.log(a.length);  //返回2，说明仅有两个元素有效
console.log(a[0]);  //返回3
console.log(a[1]);  //返回3

JavaScript treats the subscript of a two-dimensional array as a comma expression, and the return value of its operation is the last value. The assignments in the first two lines of code are overwritten by the assignments in the next two lines of code. Therefore, if the subscript value is determined after calculation and then the access operation is performed, the design can be carried out as follows.

var a = [], i = 1;  //初始化变量
while(i < 10) {  //指定循环次数
    a[i *= 2, i] = i;  //指定下标为2的幂数时才进行赋值
}
console.log(a.length);  //返回17
console.log(a);  //返回数组[,,2,,4,,,,8,,,,,,,,16]

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