tripal/tripal_core/theme/js/tripal.js

if (Drupal.jsEnabled) {

   function tripal_get_base_url() {

       // Get the base url. Drupal can not pass it through a form so we need 
       // to get it ourself. Use different patterns to match the url in case
       // the Clean URL function is turned on
       var baseurl = location.href.substring(0,location.href.lastIndexOf('/?q=/node'));
       if(!baseurl) {
         var baseurl = location.href.substring(0,location.href.lastIndexOf('/node'));
       }
       if (!baseurl) {
         // This base_url is obtained when Clena URL function is off
         var baseurl = location.href.substring(0,location.href.lastIndexOf('/?q=node'));
       }
       if (!baseurl) {
         // The last possibility is we've assigned an alias path, get base_url til the last /
         var baseurl = location.href.substring(0,location.href.firstIndexOf('/'));
       }
       return baseurl;
   }  
}