快速排序算法

<script type="text/javascript">
        var arr=[1,5,2,9,8,3,65,75,6,56,1];
        function quickArr(arr){
            var left=[],
                right=[],
                mid=[];
            if(arr.length<=1){
                return arr;
            }
            //var pIndex = Math.floor(arr.length/2);
            var pIndex = arr.length-1;
            var p = arr[pIndex];
            //arr.pop(p);
            for (var i = 0; i < arr.length; i++){
                if(arr[i]<p){
                    left.push(arr[i]);
                }else if(arr[i]>p){
                    right.push(arr[i]);
                }else{
                    mid.push(p);
                }
            }
            //arr.push(p);
            return quickArr(left).concat(mid,quickArr(right));
        }


        console.log(quickArr(arr))
</script>