title: add class to button after select - jquery
body: <p>I have a submit button which is disabled until a user chooses from a select list.</p>
  
  <p>I want to remove the disabled attribute and also add a class so the button becomes the standard button class I use throughout the site, on change of the select list.</p>
  
  <p>I am trying the following:</p>
  
  <pre><code>$(document).ready(
  function(){
      $('#category').change(
          function(){
              if ($(this).val()) {
                  $('input:submit').attr('disabled',false);
                  $('#btn_show').addClass.attr('button green');
  
              }
          });
  
  });
  </code></pre>
  
  <p>#category is the drop-down id and #btn_show is the button id</p>
  
  <p>The disabled is removed ok but the class not added. Is my logic correct?</p>
  
  <p>Also, is it also possible to change the value of the submit button when this change happens too?</p>