// replace array with string concatenation for better performance function quickSort(list) { if (!list.length) return []; var left = [], right = [], center = list[0]; for (var i = 1; i < list.length; i++) { if (list[i] < center) { left.push(list[i]); } else { right.push(list[i]); } }; return quickSort(left) + center + ',' + quickSort(right); }