Simple required field validator (jQuery)

HTML

<form id="form1">
  <input type="text" id="input1" required /><br />
  <textarea id="textarea1" required></textarea><br />
  <button type="submit" disabled>
  Submit
  </button>
</form>

JavaScript

$(document).on('change keyup', '[required]', function() {
		var targetForm = $($('[required]')[0].form);
		var requiredOk = targetForm.find('[required]').filter(function () { return $(this).val().length == 0; }).length == 0;
		targetForm.find(':submit').prop('disabled', !requiredOk);
});