CustomElementRegistry: метод get()

get(name)

customElements.define(
  "my-paragraph",
  class extends HTMLElement {
    constructor() {
      let templateContent = document.getElementById("custom-paragraph").content;
      super() // returns element this scope
        .attachShadow({ mode: "open" }) // sets AND returns this.shadowRoot
        .append(templateContent.cloneNode(true));
    }
  },
);

// Return a reference to the my-paragraph constructor
let ctor = customElements.get("my-paragraph");