Spot the bug - #36

programming web dev
1

Can you spot the form bug?

<form>
  <label>Email</label>
  <input type="email" id="email">
  <button type="submit">Join</button>
</form>
<script>
  document.querySelector('form').addEventListener('submit', (e) => {
    if (!email.value.includes('@')) alert('invalid');
  });
</script>

Reply with what is broken and how you would fix it.

1 Like
2

Two things are broken: you never stop the submit, and you’re relying on email magically existing as a global from id="email". Call e. preventDefault() when invalid, and grab the input explicitly:

const emailEl = document.querySelector('#email');
document.querySelector('form').addEventListener('submit', (e) => {
  if (!emailEl.value.includes('@')) {
    e.preventDefault();
    alert('invalid');
  }
});

That “id becomes a global variable” behavior is inconsistent across browsers and gets weirder once you have multiple forms/components on a page.