How to create empty 2d array in javascript?

Question

How do I create an empty 2D array in Javascript (without knowing how many rows or columns there will be in the new array)?

If it's a simple array var newArray = new Array(); I can assign as many elements as I want. But what about a 2D array? Can I create one without specifying the numbers of rows and columns? and how do I access the elements afterwards (myArray[0][1] or myArray[0,1])?

Answer 1

You can create a 6 x 6 empty array like this:

var myGrid = [...Array(6)].map(e => Array(6)); 

• Array(6) generates an array with length = 6 and full of undefined values.
• We map that array to another array full of undefined values.
• In the end, we get a 6x6 grid full of undefined positions.

If you need to initialize the grid with a default value:

var value = 'foo'; // by default var myGrid = [...Array(6)].map(e => Array(6).fill(value)); 

Now you have a 6 x 6 grid full of 'foo'.