JavaScript QuickSort Impl

QuickSort.js

function getRandomNumber(min, max) {
    return Math.round(Math.random() * (max - min) + min);
}

function lessThan(a, b) {
    return a < b;
}

function comparator(predicate) {

    return function (a, b) {

        if (predicate(a, b)) {
            return -1;
        } else if (predicate(b, a)) {
            return 1;
        } else {
            return 0;
        }
    }
}

function swap(list, a, b) {
    var temp = list[a];
    list[a] = list[b];
    list[b] = temp;
}

function middle(lo, hi) {
    return Math.floor((hi + lo) / 2);
}

function partition(list, comparator, lo, hi) {

    var pivot = list[middle(lo, hi)];

    while (lo <= hi) {

        while (comparator(list[lo], pivot) < 0) lo++;
        while (comparator(list[hi], pivot) > 0) hi--;

        if (lo <= hi) {
            swap(list, lo++, hi--);
        }
    }

    return lo;
}

function quickSort(list, comparator) {

    function _quickSort(result, comparator, lo, hi) {

        if (list.length > 1) {

            var index = partition(result, comparator, lo, hi);

            if (lo < index - 1) {
                _quickSort(result, comparator, lo, index - 1, result);
            }

            if (index < hi) {
                _quickSort(result, comparator, index, hi);
            }
        }

        return result;
    }

    return _quickSort(list.slice(), comparator, 0, list.length - 1);
}

var list = _.range(50).map(function () {
    return getRandomNumber(0, 100);
});

console.clear();
console.info('%c ' + list, 'color: red');

console.time('quicksort');
var result = quickSort(list, comparator(lessThan));
console.timeEnd('quicksort');
console.info('%c ' + result, 'color: green');

console.time('sort');
var result = list.sort(comparator(lessThan));
console.timeEnd('sort');
console.info('%c ' + result, 'color: green');