title: JQuery addClass not working
body: <p>I have a code that show and hide a div and when the div is opened or closed the opacity and color changes. Instead of using JQuery .css() to add CSS directly to the element, I want to use addClass, but I cannot figured out why code below is not working. </p>
  
  <p>I am getting the message <em>'ReferenceError: $ is not defined'</em> when I run the build. I am not sure what that means either. Help please.</p>
  
  <p><strong>JQuery</strong></p>
  
  <pre><code>$(document).ready(function() {
      $(".upload-panel-container").click(function(e) {
          $(".upload-menu-container").toggleClass("open").slideToggle(100, "linear");
          if ($(".upload-menu-container").hasClass("open")) {
              $(".upload-panel-container").addClass("setOpacityto1");
          } else {
              $(".upload-panel-container").addClass("setOpacityto85");
          }
      });
  
  });
  </code></pre>
  
  <p><strong>CSS</strong></p>
  
  <pre><code>.setopacityto1 {
      opacity: 1;
      color: red;
  }
  
  .setopacityto85{
      opacity: .85;
      color: blue;
  }
  </code></pre>