Simple quicksort implementations

qsort.js

// The simplest implementation I can write.

function qsort(array) {

    var lower, upper, pivot;

    if (array.length <= 1) {
        return array;
    }

    pivot = array.pop();

    lower = array.filter(function (value) {
        return value <= pivot;
    });

    upper = array.filter(function (value) {
        return value > pivot;
    });

    return qsort(lower).
            concat([pivot]).
            concat(qsort(upper));
}


// In-place, still simple. Not as readable.

function qsort_ip(array) {

    function partition(array, p, q) {

        var pivot = array[p],
            i = p,
            swap;

        for (j = p + 1; j < q; j++) {
            if (array[j] < pivot) {
                i++;
                swap     = array[i];
                array[i] = array[j];
                array[j] = swap;
            }
        }

        swap     = array[p];
        array[p] = array[i];
        array[i] = swap;

        return i;
    }

    function qsort_in_place(array, start, end) {

        var pivot;

        if (start < end) {

            pivot = partition(array, start, end);
            qsort_in_place(array, start, pivot);
            qsort_in_place(array, pivot + 1, end);
        }
    }

    qsort_in_place(array, 0, array.length);
}

nice, thanks :D