常用于约束一个函数及其函数的内外部属性：

    1. interface ICounter {
    2.   (start: number): void,
    3.   value: number,
    4.   interval: number,
    5.   add(): void,
    6.   reset(): number,
    7. }
    8. function generateCounter(): ICounter {
    9.   let originValue = 0;
    10.   let counter = (function (start) {
    11.     originValue = start;
    12.     counter.reset();
    13.   }) as ICounter;
    14.   counter.add = function () {
    15.     counter.value += counter.interval;
    16.   }
    17.   counter.reset = function () {
    18.     counter.interval = 1;
    19.     return counter.value = originValue;
    20.   }
    21.   return counter;
    22. }
    23. const myCounter: ICounter = generateCounter()
    24. console.log(myCounter)
    25. /**
    26. [Function: counter] {
    27.   add: [Function (anonymous)], 
    28.   reset: [Function (anonymous)]
    29. }
    30.  */
    31. myCounter(0)
    32. console.log(myCounter)
    33. /**
    34. [Function: counter] {
    35.   add: [Function (anonymous)], 
    36.   reset: [Function (anonymous)],
    37.   interval: 1,
    38.   value: 0
    39. }
    40.  */
    41. myCounter.add()
    42. console.log(myCounter)
    43. /**
    44. [Function: counter] {
    45.   add: [Function (anonymous)], 
    46.   reset: [Function (anonymous)],
    47.   interval: 1,
    48.   value: 1
    49. }
    50.  */
    51. myCounter.interval = 2
    52. console.log(myCounter)
    53. /**
    54. [Function: counter] {
    55.   add: [Function (anonymous)], 
    56.   reset: [Function (anonymous)],
    57.   interval: 2,
    58.   value: 1
    59. }
    60.  */
    61. myCounter.add()
    62. console.log(myCounter)
    63. /**
    64. [Function: counter] {
    65.   add: [Function (anonymous)], 
    66.   reset: [Function (anonymous)],
    67.   interval: 2,
    68.   value: 3
    69. }
    70.  */
    71. myCounter.reset()
    72. console.log(myCounter)
    73. /**
    74. [Function: counter] {
    75.   add: [Function (anonymous)], 
    76.   reset: [Function (anonymous)],
    77.   interval: 1,
    78.   value: 0
    79. }
    80.  */