SOURCE

const arr = [5, 3, 7, 1, 4, 2, 2, 1, 9];

function quickSort(list) {
    if (list.length <= 1) {
        return list;
    }

    const left = [];
    const right = [];
    const target = list.shift();

    for (let i = 0; i < list.length; i++) {
        if (list[i] <= target) {
            left.push(list[i]);
        }
        else {
            right.push(list[i]);
        }
    }

    return quickSort(left).concat(target, quickSort(right));
}

console.log(quickSort(arr));