javascript - Ruby on Rails with Showdown adding extensions error -

i have code directly from:

https://github.com/coreyti/showdown

i created extensions dir , added twitter.js following code:

var demo = function(converter) {   return [   // replace escaped @ symbols   { type: 'lang', regex: '\\@', replace: 'red' } ]; } 

on page have:

<%= javascript_include_tag "showdown" %> <%= javascript_include_tag "extensions/twitter.js" %>  <script type="text/javascript">   var converter = new showdown.converter({ extensions: 'twitter' }); </script>  <script type="text/javascript">   $('#design_description').keyup(function () {   var converter = new showdown.converter();   var impt = converter.makehtml($(this).val());   $(".preview").html(impt); }); </script> 

this web console error getting:

[15:04:30.945] uncaught exception: extension 'undefined' not loaded. either not found or not valid extension.

any appreciated.

wrap demo function:

(function(){      var demo = function(converter) {         return  [           // replace escaped @ symbols           { type: 'lang', regex: '\\@', replace: 'red' }         ];     };      // client-side export     if (typeof window !== 'undefined' && window.showdown && window.showdown.extensions) { window.showdown.extensions.demo = demo; }     // server-side export     if (typeof module !== 'undefined') module.exports = demo;  }());