Function connectedCallback

packages/reactive-element/src/reactive-element.ts:1137–1143

* On first connection, creates the element's renderRoot, sets up * element styling, and enables updating. * @category lifecycle

()

   * @category lifecycle
   */
  connectedCallback() {
    // Create renderRoot before controllers `hostConnected`
    (this as Mutable<typeof this, 'renderRoot'>).renderRoot ??=
      this.createRenderRoot();
    this.enableUpdating(true);
    this.__controllers?.forEach((c) => c.hostConnected?.());
  }

  /**
   * Note, this method should be considered final and not overridden. It is