js实现快速排序

非原创：

var quickSort = function(arr){
 
     if(arr.length<=1){return arr;}
 
     var pivotIndex = Math.floor(arr.length/2);
     var pivot = arr.splice(pivotIndex,1)[0];
 
     var left = [];
     var right = [];
 
     for(var i=0;i<arr.length;i++){
         if(arr[i]<pivot){
             left.push(arr[i]);
         }else{
             right.push(arr[i]);
         }
     }
    return quickSort(left).concat([pivot],quickSort(right))    ;
 
};
 
var arr = [5,100,6,3,-12];
document.write(quickSort(arr));