How to fix Apps Script file loading order and defintion visibility problems with an Exports object.
It’s good practice to keep class and namespace definitions in separate files and avoid defining functions or variables in the global space. However, App Script doesn’t give you control over the order in which it loads files. If you reference a class or a namespace from one script file, it may not yet be defined. This is where an Exports object comes in.
As your script projects get larger and you start splitting out across script files you may find you need a little more structure. Class and namespace definitions are a good way to structure your code. Even when you do this you can still encounter problems with parts of your script trying to run before they are fully loaded.
This was a particular issue when the V8 runtime launched in 2020. This was fixed in June 2022, but it can still be an issue depending on how declarations are made in your code. To find out more about why this happens and how to fix it this post by Bruce Mcpherson shows how an Exports object can be used to structure your code.
Source: Fix Apps Script file order problems with Exports – Desktop Liberation
Member of Google Developers Experts Program for Google Workspace (Google Apps Script) and interested in supporting Google Workspace Devs.