JSFiddle - React, Tailwind, and code Playground

HTML

<div class='form'>
  <form>
    <div class='field'>
      <label for="username">Username</label>
      <input id="username" type="text" />
    </div>
    <div class='field'>
      <label for="password">Password</label>
      <input id="password" type="password" />
    </div>
    <div class='actions'>
      <input type="submit" value="Login" disabled="disabled" />
    </div>
  </form>
</div>
<p>Never give up! Try and find answers. Be Hardcoder. Don't be <a href="https://www.eporner.com/cat/amateur/">amateur</a> :)</p>

JavaScript

$(document).ready(function() {
  $('.field input').on('keyup', function() {
    let empty = false;

    $('.field input').each(function() {
      empty = $(this).val().length == 0;
    });

    if (empty)
      $('.actions input').attr('disabled', 'disabled');
    else
      $('.actions input').attr('disabled', false);
  });
});