How to pass parameters to a custom event through js file?

Summary

How to pass parameters to a custom event through js file?

Content

Hi, 

I created a custom event and an action chain with it that has a CallModuleFunction Action in it which calls a Module function that takes an input argument.

I am using EventHelper to call the Custom Event from the js file. Below is my code:-

  this.eventHelper = context.getEventHelper();
  this.eventHelper.fireCustomEvent("setCookieOnClickEvent", "en-US");  //Passing en-US to set as function param val called in action chain

I want to trigger the "setCookieOnClickEvent" event & pass the 2nd parameter to the input argument of the method selected in CallModuleFunction action.. but this doesn't work..the argument comes as undefined.