...
The record cannot be empty, in such a case Unity will show you an error: “The interceptor with name pfxInterceptor_myFirstExperiment was not found”.
Basic
Step 1
Interceptors are written in plain JavaScript.
...
You don't need to implement both variants. In some cases only the PRE action makes sense, for others it is only the POST action. TBD - Explain where to use PRE & POST
Function Parameters
When Unity triggers a function which is in your exported constant, it will pass an object parameter to it. This object contains API functions and data related to the triggered action.
...