Create a 2-dimensional Array in JavaScript

When I tried to create a two-dimensional array today, I surprisingly discovered that there is no built-in function which can help us to create two-dimensional array in JavaScript.

I searched online and people suggested several ways to do so.

The simpliest I’ve found is to initialize the array with some random numbers:

var array = [[1], [1]];

Then you may alter the array based on your needs. However sometimes the size of the array is fixed, such as question “Unique Paths” on Leetcode. We need an array of size m x n for dynamic programming. And we need to change the value inside based on index.

If we used the example above, we would have to make a test if the size of the array is still OK. If yes, append new number in this sub-array; while if no, append a new sub-array, then append number into the new sub-array. It would be a lot of hassle with this method. So there is another way of creating an array with preset size:

var array = new Array(m);
for (var i = 0; i < m; i++) {
array[i] = new Array(n);