examples/fundamentals__errors/index.html

<html lang="en">
  <body>
    <main>
      <h1>Handling application errors</h1>
      <p>
        Click on the button to cause application error
        <button id="error">Throw an error</button>
      </p>

      <p>
        This button tells the application to create an unhandled rejected promise
        <button id="promise">Unhandle</button>
      </p>
    </main>
    <script src="app.js"></script>
  </body>
</html>