By clicking the call button, you can have the xajax enabled function invoke the function from the server. The function, if present, will pop up an alert indicating that it was called.
The wrap button will cause the xajax enabled function to generate a function wrapper around the existing javascript function. The wrapper function will pop up an alert message before calling the original function, then another alert message once the function returns. The wrapper function can be added around the original function any number of times. Each time the wrapper function is applied, it will add a new "layer" where the before and after alert messages are displayed. Click the call button after wrapping the function to see the result.