Interview question

question.ts

// Timer interview question
// https://twitter.com/erikras/status/1560681872002277379

class Timer {
  q = Promise.resolve()

  call(cb) {
    this.q = this.q.then(() => cb())
    return this
  }

  waitFor(seconds) {
    this.q = this.q.then(() => new Promise((resolve) => setTimeout(resolve, seconds * 1000)))
    return this
  }
}

new Timer()
  .call(() => console.log('Wait for 2 seconds'))
  .waitFor(2)
  .call(() => console.log('Wait for 3 seconds'))
  .waitFor(3)
  .call(() => console.log('Done'))