用JS实现快速排序

function quickSort(arr){

    if(arr.length<=1){
        return arr;
    }
    
    var num = Math.floor(arr.length/2);
    
    var numValue = arr.splice(num,1);
    
    var left = [];
    var right = [];
    
    for(var i=0;i<arr.length;i++){
        if(arr[i]<numValue){
            left.push(arr[i]);
        }
        else{
            right.push(arr[i]);
        }
    }
    
    return quickSort(left).concat([numValue],quickSort(right));

}


alert(quickSort([12,5,37,6,22,40]));