Shadow DOM

Backed(class CoolElement extends HTMLElement {
  created() {
    // When on Custom Elements V0, attachShadow will actually call createShadowRoot().
    this.root = this.attachShadow({mode: 'open'});
    this.root.innerHTML = '<slot></slot>';
  }
  
  connected() {
    this.innerHTML = 'Hello world!';
  }

  ready() {
    // Backed is finished, all properties & attributes are set
  }
});