qsort

qsort.js

function qsort(arr) {
    partition(arr, 0, arr.length - 1);
}

function partition(arr, left, right) {
    // check terminate
    if (left >= right) return;

    // select a pivot, for simplicity select the right most one
    var pivot = arr[right];
    var pos = left;
    // loop, pos must be the index that arr[pos] >= pivot,
    // and all the left side of arr[pos] arr <= pivot
    // all the right side of arr[pos] >= pivot
    for (var i = left; i < right; i++) {
        if (arr[i] <= pivot) {
            swap(arr, i, pos);
            pos++;
        }
    }
    swap(arr, right, pos);
    partition(arr, left, pos - 1);
    partition(arr, pos + 1, right);
}

function swap(arr, a, b) {
    var temp = arr[a];
    arr[a] = arr[b];
    arr[b] = temp;
}
a = [3, 5, 7, 1, 99, 10, 23, 67];
qsort(a);
console.log(a);