Increment/Decrement Function with Firebase v9.1 Realtime Database using JavaScript

I am looking for a developer to create an Increment/Decrement Function with Firebase v9.1 Realtime Database using JavaScript. The expected behavior of the function is to increment or decrement a specific value by a user-defined amount. There is no specific frontend framework required for this project. Additionally, no authentication or authorization is needed for the function. The ideal candidate for this job should have experience with Firebase v9.1 Realtime Database, JavaScript, and creating functions.