LazyMan

class LazyMan {
  constructor() {
    this.queue = Promise.resolve();
  }
  sleep(timer) {
    this.queue = this.queue.then(() => {
      return new Promise(resolve => {
        console.log('sleeping,wait:' + timer + 's');
        setTimeout(() => {
          resolve();
        }, timer * 1000);
      });
    });
    return this;
  }
  eat(fruit) {
    this.queue = this.queue.then(() => {
      return new Promise(resolve => {
        console.log('eat:' + fruit);
        resolve();
      });
    });
    return this;
  }
}
let person = new LazyMan();
person
  .sleep(3)
  .eat('banana')
  .sleep(5)
  .eat('peach');

class Person {
  constructor() {
    this.queue = [];
    setTimeout(() => {
      this.next();
    }, 0);
  }
  sleep(timer) {
    return this.subscribe(() => {
      return new Promise(resolve => {
        console.log('sleeping,wait:' + timer + 's');
        setTimeout(() => {
          resolve();
        }, timer * 1000);
      });
    });
  }
  eat(fruit) {
    return this.subscribe(() => {
      console.log('eat' + fruit);
    });
  }
  subscribe(fn) {
    this.queue.push(async () => {
      try {
        fn && (await fn());
      } catch (error) {
        console.error('方法执行失败', { fn, error });
      }
      this.next();
    });
    return this;
  }
  next() {
    const fn = this.queue.pop();
    fn && fn();
  }
}
let person = new Person();
person
  .sleep(3)
  .eat('banana')
  .sleep(5)
  .eat('peach');