冒泡排序

 for (var i = 0; i < arr.length - 1 - i; i++) {

            //每轮比较多少次

            for (var j = 0; j < arr.length - 1; j++) {

                if (arr[j] > arr[j + 1]) {

                    //位置交换  把arr[j+1]变成大值

                    var temp = arr[j]

                    arr[j] = arr[j + 1]

                    // j   大  j+1 小

                    // j+1 大  j   小

                    arr[j + 1] = temp

                }

            }

        }

        console.log(arr)