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();//The pop() method removes the last element of an array, and returns that element.

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

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

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