数组去重算法，quickSort

function removeRepeat(arr) {
    var arr2 = [] ,obj = {};
    for (var i = 0; i<arr.length;  i++) {  
        var num = arr[i];    //先把arr的第[i]num
             if( !obj[num] ){    //如果上面有个true，那么就不要push进数组，否则就push进数组
             arr2.push(num);
         obj[num] = true;  //不要忘记push到数组以后把obj上的属性设置为true，那么下次有一样的属性就不会进来了
          }
    }
    console.log(arr2);
}
removeRepeat([1,2,5,2,1,5,5,2,1,1,5,2,2,5,1]);

var quickSort = function(arr) {　　
    if (arr.length <= 1) {
        return arr;
    } else {
        //split for center 
        var pivotIndex = Math.floor(arr.lenght / 2);
        //get center value
        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]);
        }
        }
     }
    //call me loop
    return quickSort(left).concat([pivot], quickSort(right));
};