quickSort.js

var a = ['S', 'O', 'R', 'T', 'E', 'X', 'A', 'M', 'P', 'L', 'E'];

function qSort(from, to) {
    if (from >= to) {
        return;
    }
    var pivot = a[to];
    var counter = from;

    for (var i = from; i < to; i++) {
        if (a[i] < pivot) {
            qSwap(i, counter);
            counter++;
        }
    }
    qSwap(counter, to);
    qSort(from, counter - 1);
    qSort(counter + 1, to);
}

function qSwap(x, y) {
    let temp = a[x];
    a[x] = a[y];
    a[y] = temp;
}

qSort(0, a.length - 1);
console.log(a);