index.html

<!DOCTYPE html>
<html>
  <head>
    <title>Leds</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <link rel="stylesheet" href="assets/css/checkbox.css">
  </head>
  <body>
    <div class="container">
      <h1 class="text-center">Leds</h1>

      <div class="wrap-checkbox danger">
        <input type="checkbox" name="red" id="led9" class="js-check" disabled>
        <label for="led9"></label>
      </div>

      <div class="wrap-checkbox warning">
        <input type="checkbox" name="yellow" id="led11" class="js-check" disabled>
        <label for="led11"></label>
      </div>

      <div class="wrap-checkbox success">
        <input type="checkbox" name="green" id="led13" class="js-check" disabled>
        <label for="led13"></label>
      </div>

    <script src="/socket.io/socket.io.js"></script>
    <script src="assets/js/app.js"></script>
  </body>
</html>