javascript快速排序

function quickSort(arr){

  if(arr.length <= 1) return arr;//判断是否有效数组

  var cut = Math.floor(arr.length/2);//取中间下标

  var left = [],right = [];

  var num = arr.splice(cut,1)[0];//取基准值

  for(var i = 0;i < arr.length;i ++){

    if(arr[i] < num){

      left.push(arr[i]);//小的放左边

    }else {

      right.push(arr[i]);//大的放右边

    }

  }

  return quickSort(left).concat(num,quickSort(right));//递归

}