1. 实现一个LazyMan，可以按照以下方式调用:
    2. LazyMan(“Hank”)输出:
    3. Hi! This is Hank!
    5. LazyMan(“Hank”).sleep(10).eat(“dinner”)输出
    6. Hi! This is Hank!
    7. //等待10秒..
    8. Wake up after 10
    9. Eat dinner~
    11. LazyMan(“Hank”).eat(“dinner”).eat(“supper”)输出
    12. Hi This is Hank!
    13. Eat dinner~
    14. Eat supper~
    16. LazyMan(“Hank”).eat(“supper”).sleepFirst(5)输出
    17. //等待5秒
    18. Wake up after 5
    19. Hi This is Hank!
    20. Eat supper
    22. /* 分析思路：
    23.   1，实现链式调用，可调用方法 都会返回 this 也就是 new 出来的实例对象；
    24.   2，实现延迟调用；
    25.   3，可自定义任务优先调用
    26. */
    1. class LazyMan {
    2.   constructor(name) {
    3.     this.tasks = []
    4.     const task = () => {
    5.       console.log('Hi! This is ' + name)
    6.       this.next()
    7.     }
    9.     this.tasks.push(task)
    11.     // 重点，下一次需执行的宏任务，触发任务入口
    12.     setTimeout(() => {
    13.       this.next()
    14.     }, 0)
    15.   }
    17.   // next ??? 依次执行任务队列中的任务
    18.   next() {
    19.     const task = this.tasks.shift()
    20.     task && task()
    21.   }
    23.   sleep(time) {
    24.     this._sleepWrapper({ time, isFirst: false })
    25.     return this
    26.   }
    28.   sleepFirst(time) {
    29.     this._sleepWrapper({ time, isFirst: true })
    30.     return this
    31.   }
    33.   _sleepWrapper({time, isFirst}) {
    34.     const task = () => {
    35.       setTimeout(() => {
    36.         console.info('Wake up after ' + time)
    37.         this.next()
    38.       }, time * 1000)
    39.     }
    40.     if(isFirst) {
    41.       this.tasks.unshift(task)
    42.     } else {
    43.       this.tasks.push(task)
    44.     }
    45.   }
    47.   eat(name) {
    48.     const task = () => {
    49.       console.log('Eat ' + name)
    50.       this.next()
    51.     }
    52.     this.tasks.push(task)
    53.     return this
    54.   }
    55. }
    57. function lazyMan(name) {
    58.   return new LazyMan(name)
    59. }
    61. // lazyMan("Hank")
    62. // lazyMan("Hank").sleep(2).eat("dinner")
    63. // lazyMan("Hank").eat("dinner").eat("supper")
    64. lazyMan("Hank").eat("supper").sleepFirst(3)