fancy-idl-indeed.js

customElements.define('any-element', class extends Element {
  get data() {
    return this.dataset;
  }
  set data(value) {
    // more or less this operation, but previously known keys,
    // not found in value, should be dropped from the dataset
    Object.assign(this.dataset, value);
  }
  get aria() {
    return [...this.attributes]
            .filter(attr => /^(?:role|aria-.*)$/.test(attr.name))
            .reduce((o, a) => ((o[a.name.replace(/^aria-/, '')] = a.value), o), {});
  }
  set aria(value) {
    // more or less this operation, but previously known
    // aria related attributes, not found in value,
    // should be dropped if not present
    Object.keys(value).forEach(key => {
      this.setAttribute(key === 'role' ? key : `aria-${key}`, value[key]);
    });
  }
});

the related tweet for historical reasons: https://twitter.com/WebReflection/status/1234901261322989570