Promise implementation

Promise impletementation.js

class MyPromise {
  constructor(executor) {
    this.state = MyPromise.states.pending
    this.queue = {
      'resolve': [],
      'reject': []
    }
    try {
      executor(this.resolver.bind(this), this.rejecter.bind(this))
    } catch (e) {
      this.rejecter(e)
    }
  }
  static get states() {
    return {
      resolve: 'resolved',
      reject: 'rejected',
      pending: 'pending'
    }
  }
  resolver(payload) {
    this.state = MyPromise.states.resolve
    let curFn
    try {
      curFn = this.queue.resolve[0](payload)
    } catch (e) {
      this.rejecter(e)
    }
    for (let i = 1; i < this.queue.resolve.length; i++) {
      if (curFn instanceof MyPromise) {
        curFn.queue.resolve.push(...this.queue.resolve.slice(i))
        break;
      }
      try {
        curFn = this.queue.resolve[i](curFn)
      } catch (e) {
        this.rejecter(e)
      }
    }
  }
  rejecter(reason) {
    this.state = MyPromise.states.reject
    this.queue.reject.forEach(el => el(reason))
  }
  then(exec = () => { }) {
    this.queue.resolve.push(exec)

    return this
  }
  catch(exec = () => { }) {
    this.queue.reject.push(exec)

    return this
  }
}

new MyPromise(function (resolve, reject) {
  setTimeout(() => {
    resolve("resolved")
    // reject('rejected')
  }, 2000);
})
  .then(payload => delay(payload))
  .then(res => console.log(`${res} second`)) // resolved first second
  // .catch(err => console.log(err))

function delay(payload) {
  return new MyPromise(resolve => {
    setTimeout(() => {
      resolve(`${payload} delay`)
    }, 2000);
  })
}