Not a Constructor error in a new Java Script

Question

I'm relatively new to Java script and I have written a simple java script like below , This is a custom java script and does not extend the already existing java script. Below is the code and when I try to test I get an error as Line 2 : TypeError: X is not a constructor TypeError: X is not a constructor

I declared a variable inside the selectX method but the constructor error came up hence I decided to remove and simply check if the code works but no luck. I'm unable to figure out what could be the issue..

Here X is the Name of the Java script that I'm trying to achieve

define("custom/handlers/X", 
    [ "dojo/_base/declare",
      "dojo/_base/array",       
      "platform/model/ModelService", 
      "platform/handlers/_ApplicationHandlerBase",
      "application/handlers/CommonHandler",
      "platform/exception/PlatformRuntimeException",
      "platform/translation/MessageService",
      "dojo/_base/lang",
      "platform/util/PlatformConstants,"
      "platform/auth/UserManager"
      ],
function(declare, array, ModelService, ApplicationHandlerBase, CommonHandler, 
PlatformRuntimeException, MessageService, UserManager){
return declare ( [ApplicationHandlerBase], {                
            selectX: function(eventContext){


             }

         });
});