title: Uncaught TypeError : cannot read property 'prototype' of undefined
body: <p>Have got a problem with the JavaScript of a Wordpress plug-in that I am using. </p>
  
  <p>Here is my code: </p>
  
  <pre><code>(function ($) {
      $.extend($.slidewizard.prototype, {
          _options_default: function (opts) {
              return opts;
          }
      });
  })(jQuery);
  </code></pre>
  
  <p>I've got a lot of JS/jQuery in my website and I think there is a conflict between them.
  My console said: </p>
  
  <blockquote>
    <p>Uncaught TypeError : cannot read property 'prototype' of undefined</p>
  </blockquote>
  
  <p>Any ideas?</p>