js 快速排序

<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<script type="text/javascript">
		window.onload = function (){
			var arr = [34,7,3,11,20,40,13,5];

		function quickSort(arr){

			if(arr.length <= 1){
				return arr;
			}

			var num = arr[Math.ceil(arr.length/2 - 1) ];

			var arrL = [];
			var arrC = arr.splice(num,1);
			var arrR = [];

			for(var i = 0; i < arr.length; i++){
				if(arr[i] < num){
					arrL.push( arr[i] );
				}
				else if( arr[i] > num ){
					arrR.push( arr[i] )
				}else{
					arrC.push(arr[i]);
				}
			}

			return quickSort( arrL ).concat( arrC , quickSort( arrR ) );
		}

		console.log(quickSort( arr ));
			}
	</script>

</head>
<body>

</body>
</html>