[Nexus]

<form>
<button type="submit">Submit</button>
</form>

<input type="file"/>

<script>
  const form = document.querySelector('form');
  const fileInput = document.querySelector('[type="file"]');

  form.addEventListener('submit', e => {
    e.preventDefault();

    alert(fileInput.files.length ? `Name of chosen file: ${fileInput.files[0].name}` : 'Choose file');
  });
</script>