async constructors

index.js

class Car {
  constructor() {
    return Promise.resolve(this.new())
  }

  async new() {
    await this.sleep(1000)
    this._wheels = 4
    return this
  }

  wheels() {
    return this._wheels || 2
  }

  sleep(ms) {
    return new Promise(resolve => {
      setTimeout(resolve, ms)
    })
  }
}

;(async () => {
  const car = await new Car()
  console.log(car.wheels())
})()