aureooms/js-array

export function product(iterables, repeat, out) {
    // Product(['ABCD', 'xy'], 1) --> Ax Ay Bx By Cx Cy Dx Dy
    // product([range(0, 2, 1)], 3) --> 000 001 010 011 100 101 110 111

    let a;
    let b;
    let i;
    let j;
    let k;
    let m;
    let n;
    let iterable;
    let c;
    let len;

    a = [[]];

    // Repeat k times

    for (k = 0; k < repeat; ++k) {
        // For each iterable
        // concatenate existing combinaisons
        // with every element of this iterable

        for (i = 0, m = iterables.length; i < m; ++i) {
            // B will contain the newly created combinaisons

            b = [];

            // Cache the current iterable

            iterable = iterables[i];

            // For each existing combinaison

            for (j = 0, n = a.length; j < n; ++j) {
                // For each element of the current iterable

                for (c = 0, len = iterable.length; c < len; ++c) {
                    // Concatenate existing combinaison with
                    // current element of the iterable

                    b.push(a[j].concat(iterable[c]));
                }
            }

            // Update a for next round

            a = b;
        }
    }

    // Report output

    for (j = 0, n = a.length; j < n; ++j) {
        out.push(a[j]);
    }

    return out;
}