popup.html

<!doctype html>
<html>
  <head>
    <title>Javascript Injector</title>
    <link rel="stylesheet" href="/lib/bootstrap.min.css" crossorigin="anonymous">
    <link rel="stylesheet" href="/lib/styles.css">
    <script src="/lib/jquery-3.2.1.min.js"></script>
    <script src="data.js"></script>
    <script src="popup.js"></script>
  </head>
  <body>
    <div class="container container-fluid">
      <div class="row">
        <label for="url">For URLs (1) not matching a longer rule and (2) containing:</label>
        <textarea id="url" cols="40" rows="2"></textarea>
        <label for="jscode">Execute the following code:</label>
        <textarea id="jscode" cols="40" rows="10" placeholder="Please paste your javascript here then click on Inject."></textarea>
        <button id="inject" class="btn btn-primary">Inject</button>
      </div>
    </div>
  </body>
</html>