The best way to test this would be to add this code to your mbox.js file then download the newly created file and use an override in a tool like Charles with MapLocal to make sure your parameters are coming in as you expected.
The best way to test this would be to add this code to your mbox.js file then download the newly created file and use an override in a tool like Charles with MapLocal to make sure your parameters are coming in as you expected.