• 方式一 ```javascript function fn(){ var num = 0;

      function add(){ num ++; console.log(num); };

      function sub(){ num —; console.log(num); }

      return [add, sub]; }

    var test = fn() test0; test1;

    2. - 方式二
    3. ```javascript
    4. function fn(){
    5.   var num = 0;
    7.   var compute = {
    8.     add: function(){
    9.       num ++;
    10.       console.log(num);
    11.     },
    13.     sub: function(){
    14.       num --;
    15.       console.log(num);
    16.     }
    17.   }
    19.   return compute;
    20. }
    22. var test = fn()
    24. test.add();
    25. test.sub();

    • 方式三 ```javascript function fn(){ var num = 0;

      this.add = function(){ num ++; console.log(num); };

      this.sub = function(){ num —; console.log(num); } }

    var test = new fn();

    test.add(); test.sub();

    因为new时fn函数会默认return this 如果手动在fn函数最后return 原始值，不会影响，return 引用值，则会影响； ```