hogeWidget.js

export default class HogeWidget {
  constructor(el, resolver) {
    this.el = el;
    this.resolver = resolver;
  }
  bind() {
    this.el.addEventListener('click', () => { ... });
  }
  init() {
    this.bind();
    // 何か非同期な処理
    setTimeout(() => {
      this.resolver();
    }, 1000);
  }
}

/*
<div data-widget="hoge">clickable!</hoge>