Disable submit if inputs empty jquery

I use this in my project and it succes.

$(document).ready(function() {
  $('.field').keyup(function() {

    var empty = false;
    $('.field').each(function() {
        if ($(this).val().length == 0) {
            empty = true;
        }
    });                   

    if (empty) {
        $('.actions[type="submit"]').attr('disabled', 'disabled');
    } else {
        $('.actions[type="submit"]').removeAttr('disabled');
    }                
  });
});

I would suggest disabling the button by default. I would also look at the length of the .val(), not check for an empty string. Lastly, I think document.ready() is much more readable than your existing code: Here is the full code:

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>​

JS/jQuery

$(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);
  });
});

Here's a working fiddle.