zip.js

function* zip(...iterables) {
    let iterators = iterables.map(i => i[Symbol.iterator]());
    while (true) {
        let entries = iterators.map(i => i.next());
        let done = entries.some(entry => entry.done);
        if (done) break;
        yield entries.map(e => e.value);
    }
}

let zipped = zip(['a', 'b', 'c'], ['d', 'e', 'f']);
for (let x of zipped) {
    console.log(x);
}
// Output:
// ['a', 'd']
// ['b', 'e']
// ['c', 'f']

zip_no_generator.js

function zip(...iterables) {
    let iterators = iterables.map(i => i[Symbol.iterator]());
    let done = false;
    return {
        [Symbol.iterator]() {
            return this;
        },
        next() {
            if (!done) {
                let entries = iterators.map(i => i.next());
                done = entries.some(entry => entry.done);
                if (!done) {
                    return { value: entries.map(e => e.value) };
                }
            }
            // We are done
            return { done: true };
        }
    }
}

@rauschma, is there a performance benefit of one over the other? Also, how would these compare to zip_no_iterators_either or zip_old_school_loops?

http://jsperf.com/zip

I wish there was a simple jsperf that supported ES6...