[手写代码] 一个 LazyMan 是怎么养成的？

[QuocVi1994]

编程题，实现LazyMan：

• LazyMan('Hank')

• Hi! This is Hank!

• LazyMan('Hank').sleep(10).eat('dinner')

• Hi! This is Hank!
• 等待10秒
• Wake up after 10
• Eat dinner~

• LazyMan('Hank').eat('dinner').eat('supper')

• Hi This is Hank!
• Eat dinner~
• Eat supper~

• LazyMan('Hank').sleepFirst(5).eat('supper')

• 等待5秒
• Wake up after 5
• Hi This is Hank!
• Eat supper

• 每个函数都返回this，供链式调用。 • this里面建立一个调用队列，在执行LazyMan时立即setTimeout(()=>顺序执行调用栈内容)，确保链式调用完之后会开始执行调用栈内容。 • 根据函数的优先级去放入调用队列的前面或后面，如sleepFirst在前，sleep在后。 • 顺序执行调用栈时可被阻塞，如sleepFirst的函数执行后会返回一个Promise，然后调用栈发现是Promise则进行await，等待resolve之后才执行下一个函数。

[QuocVi1994]

这是一道很经典的面试题，包括微信也曾问到过这种题目。

[QuocVi1994]

class _LazyMan {
  constructor (name) {
    this.taskQueue = [];
    this.runTimer = null;
    this.sayHi(name);
  }

  run () {
    if (this.runTimer) {
      clearTimeout(this.runTimer);
    }

    this.runTimer = setTimeout(async () => {
      for (let asyncFun of this.taskQueue) {
        await asyncFun()
      }
      this.taskQueue.length = 0;
      this.runTimer = null;
    })
    return this;
  }

  sayHi (name) {
    this.taskQueue.push(async () => console.log(`Hi, this is ${name}`));
    return this.run();
  }

  eat (food) {
    this.taskQueue.push(async () => console.log(`Eat ${food}`));
    return this.run();
  }

  sleep (second) {
    this.taskQueue.push(async () => {
      console.log(`Sleep ${second} s`)
      return this._timeout(second)
    });
    return this.run();
  }

  sleepFirst (second) {
    this.taskQueue.unshift(async () => {
      console.log(`Sleep first ${second} s`)
      return this._timeout(second);
    });
    return this.run();
  }

  async _timeout (second) {
    await new Promise(resolve => {
      setTimeout(resolve, second * 1e3);
    })
  }
}

var lazyMan = name => new _LazyMan(name)

lazyMan('fucker').sleep(4).eat(`you`)