Does App maker has any debugging options on the JavaScript functions. I can see debugging options in google script.
When I tried to run functions it shows the error in the logger, it is not enough to identify the exact issue. If there is a default debugging option it will be easy to identify the issue
There are different debugging techniques for App Maker and they are different for Server and Client scripts.
Client Script debugging:
Write 'debugger;' statement in code where you need to break, redeploy app, open Browser Dev Tools and reload app. It is just a basic JS debugging technique.
You can use 'console.log()' to put some messages to browser's console.
Server Script debugging:
You can use 'console.log()' to put some messages to browser's console (this will work only if you are deployment owner, otherwise you'll not see these messages).
You can use 'console.log()' and see your messages in Google Cloud Platform logs for your Deployment:
or Preview: