SOURCE

class Lazy {
  constructor(name) {
    this.sleepFirstTime = 0;
    this.promise = Promise.resolve().then(
      () => this.sleepFirstTime && this._sleep(this.sleepFirstTime)
    ).then(() => {
      console.log(`Hi! This is ${name}!`);
    });
  }
  sleepFirst(time) {
    this.sleepFirstTime = time;
    return this;
  }
  eat(food) {
    this.promise = this.promise.then(() => {
      console.log(`Eat ${food}~`);
    });
    return this;
  }
  sleep(time) {
    this.promise = this.promise.then(()=>this._sleep(time));
    return this;
  }
  _sleep(time){
    return new Promise((next) => {
      setTimeout(() => {
        console.log(`Wake up after ${time}`);
        next();
      }, time * 1000);
    });
  }
}

function LazyMan(name) {
  return new Lazy(name);
}

console.log('start:');
LazyMan("Hank").eat('cake').sleepFirst(3).sleep(5).eat("dinner").sleep(3).eat('supper');