@extra-array/cartesian-product/index.js

Lists cartesian product of arrays.

'use strict';
function id(v) {
    return v;
}
function cartesianProduct(xs, fm = null) {
    var fm = fm || id;
    var X = xs.length, a = [];
    if (X === 0)
        return a;
    var is = new Array(X).fill(0);
    var ls = xs.map(x => x.length);
    if (ls.some(l => l === 0))
        return a;
    for (var i = 0;; i++) {
        for (var j = 0, vs = []; j < X; j++)
            vs.push(xs[j][is[j]]);
        a.push(fm(vs, i, null));
        for (var r = X - 1; r >= 0; r--) {
            if (++is[r] < ls[r])
                break;
            is[r] = 0;
        }
        if (r < 0)
            break;
    }
    return a;
}
module.exports = cartesianProduct;