Why is it when I am doing suitecloud file:upload, it errors out with "Syntax error: missing : after property id. ". But I am able to suitecloud project:deploy. I double check my code and there seems no error.

Post the code and let someone else double check? Or try to validate it in some online tool? https://eslint.org/play

will try eslint. thanks!

I see that message when I'm trying to use object destructuring in SS2.1 but the script is flagged as 2.0 which doesn't support destructuring.

Does your deploy.xml include that script?