/*
 streaming cartesian product elements uses less memory ...
*/
const generator = cartesianProductSimplified(['a', 'b'], [1, 2, 3, 4], ['x', 'y', 'z']);
/* prints
[ 'a', 1, 'x' ]
[ 'a', 1, 'y' ]
[ 'a', 1, 'z' ]
[ 'a', 2, 'x' ]
[ 'a', 2, 'y' ]
[ 'a', 2, 'z' ]
[ 'a', 3, 'x' ]
[ 'a', 3, 'y' ]
[ 'a', 3, 'z' ]
[ 'a', 4, 'x' ]
[ 'a', 4, 'y' ]
[ 'a', 4, 'z' ]
[ 'b', 1, 'x' ]
[ 'b', 1, 'y' ]
[ 'b', 1, 'z' ]
[ 'b', 2, 'x' ]
[ 'b', 2, 'y' ]
[ 'b', 2, 'z' ]
[ 'b', 3, 'x' ]
[ 'b', 3, 'y' ]
[ 'b', 3, 'z' ]
[ 'b', 4, 'x' ]
[ 'b', 4, 'y' ]
[ 'b', 4, 'z' ]
*/
printValues(generator);

// helper function to print all values from a generator function
function printValues(generator) {
    let iteration = null;
    while (iteration = generator.next()) {
        if (iteration.done === true) {
            break;
        }
        console.log(iteration.value);
    }
}

// helper function to construct the arguments array for the 'cartesianProduct' class
function cartesianProductSimplified(...arrays) {
    let args = [];
    for (let i = 1; i < arrays.length; i++) {
        args = args.concat([cartesianProduct, arrays[i]]);
    }
    args.splice(0, 0, arrays[0]);
    return cartesianProduct(...args);
}

/*
 call it like this:
 
 cartesianProduct(['a', 'b'], cartesianProduct, [1, 2, 3, 4], cartesianProduct, ['x', 'y', 'z']);
 
 use cartesianProductSimplified to simplify it:
 
 cartesianProductSimplified(['a', 'b'], [1, 2, 3, 4], ['x', 'y', 'z'])
*/
function* cartesianProduct(values, generator, ...generatorArgs) {
    for (const value of values) {
        if (generator) {
            const iterator = generator(...generatorArgs);
            let iteration = null;
            while (iteration = iterator.next()) {
                if (iteration.done === true) {
                    break;
                }
                yield [value, ...iteration.value];
            }
        } else {
            yield [value];
        }
    }
}