JSFiddle - React, Tailwind, and code Playground

JavaScript

function matrix(m, n, initial) {
    var a, i, j, mat = [];
    for (i = 0; i < m; i += 1) {
        a = [];
        for (j = 0; j < n; j += 1) {
            a[j] = initial;
        }
        mat[i] = a;
    }
    return mat;
}

var myMatrix = matrix(4, 4, 0);
console.log(myMatrix);