JS, difference in array matrix and forEach behavior

Question

I was doing some training tasks for my JS course and I got one where you must implement a function that takes a positive integer (n) and returns a matrix like the one below

Answer 1

// your example is roughly equivalent to this.
const innerArray = new Array(n).fill(0);
const mat = new Array(n).fill(innerArray);

(mat[0] === mat[1] === innerArray) === true;

there is only 1 nested array, not n times array.