I thought initializing an multi dimensional array would be easy:
row = Array(4).fill(0)
block = Array(4).fill(row)
block[2][2] = 15
but that just creates an array of one row, 4 times, so if I assign block[2][2] = 15, then the whole column is 15.
(4) [Array(4), Array(4), Array(4), Array(4)]
0:(4) [0, 0, 15, 0]
1:(4) [0, 0, 15, 0]
2:(4) [0, 0, 15, 0]
3:(4) [0, 0, 15, 0]
I tried Array(4).fill(Array(4).fill(0)) but had the same result.
You could write a helper function to initialize your two dimensional array. For example:
const grid = (r, c) => Array(r).fill(null).map(r => Array(c).fill(null));
const g = grid(4, 4);
g[2][2] = 15;
console.log(g);
This was actually quite challenging to solve. I much prefer the accepted answer from fubar - however I thought I would add another possibility for some variance.
Pro: Doesn't obfuscate that you are dealing with an Array (like with the accepted answer).
Con: Hard to read.
var row = new Array(4).fill(0)
var block = new Array(4).fill(0).map(v => deepClone(row))
block[2][2] = 15
console.log(block);
function deepClone(array){return JSON.parse(JSON.stringify(array));}How does this work? Well after you fill the array with blank values, .map is now able to iterate each and replace the value. In this case, it is a hacky deep clone of row thanks to the trusty ole JSON.parse.
blockarray withrow, you're assigning the same object to every index.