aureooms/js-array

export function chain(iterables, out) {
    const len = iterables.length;

    if (len === 0) {
        return out;
    }

    for (let i = 0; i < len; ++i) {
        const it = iterables[i];
        const n = it.length;

        for (let j = 0; j < n; ++j) {
            out.push(it[j]);
        }
    }

    return out;
}