class AutoBindMethod {
  constructor () {
    Object.getOwnPropertyNames(this.constructor.prototype).forEach(m => {
      this[m] = this[m].bind(this)
    })
  }
}

class Demo extends AutoBindMethod {
  constructor () {
    super()
    document.addEventListener('click', this.hello)
  }
  hello () {
    console.log(this)
  }
}

new Demo()