such-java-much-script/preventDefault.html at master · seutje/such-java-much-script · GitHub

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<!doctype html>
<html lang="en">

  <head>
    <meta charset="utf-8">

    <title>Events: preventDefault</title>
    <style>
      body { border: 2px solid red; padding: 20px;}
      form { border: 2px solid green;}
      button { border: 2px solid blue;}
    </style>
  </head>
  <body>

    <form method="POST" action="">
      <input type="submit" value="click me!" />
    </form>
    <a class="toggle" href="#">toggle preventDefault();</a>
    <script>
    (function(window) {
      // Handler that calls preventDefault on the event.
      var handler = function(event) {
            if (toggler) {
              event.preventDefault();
            }
          },
          form = window.document.body.querySelector('form'),
          toggler = true;
      // The handler will effectively prevent the native submit event from happening.
      form.addEventListener('submit', handler);
      // Little toggler, using scoped toggler variable.
      window.document.body.querySelector('.toggle').addEventListener('click', function(e) {
        toggler = !toggler;
      })
    })(this);
    </script>
  </body>
</html>