JSFiddle - React, Tailwind, and code Playground

HTML

<!DOCTYPE html>
 <html>
  <head>
   <meta name="viewport" content="width=device-width, initial-scale=1">
  </head>
  <body>
   <my-element>
    <h1>This is my element</h1>
   </my-element>
  </body>
</html>

JavaScript

class MyElement extends HTMLElement {
  constructor() {
    super();
    //initializations
  }
}

customElements.define('my-element', MyElement);