Quicksort in Javascript

Quicksort in Javascript

var a = [34,2,121,4,66];
 
function quickSort(arr){
    
    if (arr.length == 0)
        return [];
 
    var left = [],
        right = [],
        pivot = arr[0];
 
    for (var i = 1; i < arr.length; i++) {
        if (arr[i] < pivot) {
           left.push(arr[i]);
        } else {
           right.push(arr[i]);
        }
    }
 
    return quickSort(left).concat(pivot, quickSort(right));
}
 
console.log(quickSort(a));