function quickSort(arr){ 
if(arr.length<1){ 
return arr; 
} 
var centerIndex = Math.floor(arr.length/2); 
var centerNum = arr.splice(centerIndex,1); 
var arrLeft = []; 
var arrRight = []; 
for(i=0;i<arr.length;i++){ 
if(arr[i]<centerNum){ 
arrLeft.push(arr[i]) 
}else if(arr[i]>centerNum){ 
arrRight.push(arr[i]) 
} 
} 
return quickSort(arrLeft).concat(centerNum,quickSort(arrRight)); 
}

function quickSort(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));
    }