Summary of bubble sort method

Sort from largest to smallest

  <script>
        /* 
        i = 0: 下标0的数组元素依次与下标为1,2,3,4的元素比,最大为arr[0]
        i= 1：下标1的数组元素依次与下标为2,3,4的元素比,得arr[1]
        ……
        i= 3：下标3的数组元素依次与下标为4的元素比,得arr[3]
        i = 4 =arr.length - 1，不执行后续循环
        
        */
        // 从大到小
        var arr = [10, 2, 5, 12, 6]
        console.log(`原始排序为${arr}`);
        for (i = 0; i < arr.length - 1; i++) { // 5个数比4趟即可
            for (j = 0; j < arr.length - 1 - i; j++) {  //每一趟的次数随着i的增加递减，所以为j < arr.length - 1 -i
                if (arr[j] < arr[j + 1]) {
                    var temp = arr[j]
                    arr[j] = arr[j+1]
                    arr[j+1] = temp

                }
            }
        }
            console.log(`由大到小的排序为${arr}`);
    </script>

code effect

Sort from smallest to largest

 <script>
  // 从小到大
        var arr = [10, 2, 5, 12, 6]
        console.log(`原始排序为${arr}`);
        for (i = 0; i < arr.length - 1; i++) { 
            for (j = 0; j < arr.length - 1 - i; j++) {  
                if (arr[j] > arr[j + 1]) {  //仅改这一步假设arr[j] > arr[j + 1]，交换变量
                    var temp = arr[j]
                    arr[j] = arr[j+1]
                    arr[j+1] = temp

                }
            }
        }
            console.log(`由小到大的排序为${arr}`);
    </script>

code effect