Javascript：将数据分配给多维数组

Question

I am trying to convert Java code to Javascript and I am trying to assign data to 3 dimensional array and I am getting "TypeError: can't convert undefined to object " error. Following is my code. Thanks in advance for any help.

var initData = [[2], [12], [2]];

for (var i = 0; i < 12; i++)
{
    initData[0][i][0] = -1;
    initData[0][i][1] = -1;
    initData[1][i][0] = -1;
    initData[1][i][1] = -1;
}

Answer 1

 [[2], [12], [2]]; 

That's not a declaration of dimensions, that's four array literals . There are no multidimensional arrays in JS. They're just one-dimensional lists that can contain arbitrary values (including other lists).

To create and fill an array that contains other arrays you have to use the following:

var initData = []; // an empty array
for (var i = 0; i < 2; i++) {
    initData[i] = []; // that is filled with arrays
    for (var j = 0; j < 12; j++) {
        initData[i][j] = []; // which are filled with arrays
        for (var k = 0; k < 2; k++) {
            initData[i][j][k] = -1; // which are filled with numbers
        }
    }
}

or, to apply your loop unrolling :

var initData = [[], []]; // an array consisting of two arrays
for (var i = 0; i < 12; i++) {
    // which each are filled with arrays that consist of two numbers
    initData[0][i] = [-1, -1];
    initData[1][i] = [-1, -1];
}

Answer 2

initData is a list of three lists, [2], [12] and [2]. Each one with one element.

In order to init a list(or array), you must do

var initData = [];

Then store in initData another list, like initData[0] = [] and so on... like it's mentioned, arrays/lists in javascript aren't initialized with a limit size.