index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <meta http-equiv="X-UA-Compatible" content="ie=edge" />
    <title>Document</title>
  </head>
  <body>
    <ul id="app"></ul>

    <script src="https://cdnjs.cloudflare.com/ajax/libs/socket.io/2.2.0/socket.io.js"></script>
    <script>
      const socket = io('http://localhost:4001');

      socket.on('connection', data => console.log(data));
      socket.on('newIdea', data => {
        console.log(data);
        document.getElementById('app').innerHTML += `
          <li>
            <div>
              <h2>${data.idea}</h2>
              <p>${data.description}</p>
            </div>
          </li>
        `;
      });
    </script>
  </body>
</html>