QuickSort.js

Array.prototype.swap = function(x,y) {
    if(x == undefined || y == undefined) return;
    var temp = this[x];
    this[x] = this[y];
    this[y] = temp;
};

var Partition = function(A,p,r) {

    var x = A[r];
    var i=p-1;

    for (var j=p; j<r;j++) {
        if(A[j]<A[r]) {
            i++;
            A.swap(i,j);
        }
    }
    A.swap(i+1,r);
    return i+1;


};

var QuickSort = function(A,p,r) {
    if (p<r) {

        var q = Partition(A,p,r);
        QuickSort(A,p,q-1);
        QuickSort(A,q+1,r);

    }
};

var arr = [null,3,4,1,2,8,6,9,5,7];
console.log(arr);

QuickSort(arr,1,9);

console.log(arr);