A quick sort example with the functional programming way of ES6 Javascript Array.prototype.quick_sort = function () { if (this.length < 2) { return this; } var pivot = this[Math.round(this.length / 2)]; return this.filter(x => x < pivot) .quick_sort() .concat(this.filter(x => x == pivot)) .concat(this.filter(x => x > pivot).quick_sort()); };