Print Elements of a Matrix in Diagonal Order

app.js

var array = [
    [[1], [2], [3], [4]],
    [[5], [6], [7], [8]],
    [[9], [10], [11], [12]],
    [[13], [14], [15], [16]],
    [[17], [18], [19], [20]]
];

function printAllDgl(array) {
    var i = 0, j = 0, output = [];
    // Loop to print each diagonal
    for (var cnt = 0; cnt < 2 * array.length - 1; cnt++) {
        if (cnt < array.length) {
            i = cnt;
            j = 0;
        } else {
            i = array.length - 1;
            j = (cnt + 1) % array.length;
        }
        while (i >= 0 && j < array.length - 1) {
            output.push(array[i][j][0])
            i--;
            j++;
        }
    }
    return output.join(',');
}

console.log(printAllDgl(array));