possibleSums

function possibleSums(coins, quantity) {
    let arr = new Set();
    for (let i = 0, clen = coins.length; i < clen; i++) {
        const coin = coins[i];
        const qty = quantity[i];
        const curr_sums = Array.from(arr);
        const curr_coins = new Array(qty).fill().map((undefined, idx) => {
            const n = coin * (idx + 1);
            arr.add(n);
            return n;
        });
        for (const s of curr_sums) {
            for (let j = 0, jlen = curr_coins.length; j < jlen; j++) {
                arr.add(curr_coins[j] + s);
            }
        }
    }
    return arr.size;
}