javascript 快速排序法实现

<script type="text/javascript">function sort(arr){   function qsort(a,low,high){if(low<high){first = low;last = high;key = a[low];while(first<last){while(first<last&&a[last]>=key){last--;}a[first]=a[last];while(first<last&&a[first]<=key){first++;}a[last]=a[first];}a[first] = key;qsort(a,low,first-1);qsort(a,first+1,high);  }    }qsort(arr,0,arr.length-1);return arr;  }  arr=[10,8,9,6,3,7,21];  var res=sort(arr);  alert(res);</script>