class MyComponent extends HTMLElement {
  constructor() {
    super();
    this.attachShadow({'mode': 'open'});
  }
  connectedCallback() {
    //Executed when the element is added to the DOM
    this.shadowRoot.innerHTML = `<p>This is my component!</p>`;
  }
  static get observedAttributes() { return []; }
  attributeChangedCallback(name, oldValue, newValue) {
    //Observe attribute changes
  }
  disconnectedCallback() {
    //Executed when the element is removed from the DOM
  }
}

customElements.define("my-component", MyComponent);