js实现快速排序

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));