How to protect XSS attacks on Google Cloud platform?

How to protect Google cloud functions from XSS attacks ?

How to validate using normal javascript if its CSRF Token based ?

please write suitable program in Node.js

When UI makes call , the program needs to generate token and send it to Ui . and Ui will send that token(i.e CSRF tokens for all calls which program makes )

Whenever it makes call , we need to validate that csrf token against which is there with us , if its valid then program should invoke automatically function user is trying to invoke