How to properly organize the joint work of the front-end and Back?

Question

Backend

Good day, ladies and gentlemen. I would like to get an answer to this question: how to properly organize the interaction between the frontend and backend when developing a project?
For example, a project has started. A part of them was prepared by the frontend and transferred to the back, but some changes are required during development. The backender decided to make such changes to the file himself and there is no correspondingly modified file on the front side.
Therefore, where can I read about the organization of projects, about the organization of the work of the frontendo and back, maybe there are articles with best practices?
UPD:
I'll try to give another example.
For example, a regular site is being developed on WordPress (any other cms). Frontend made up his part and gave it to the stretch. During the stretch, the backender made changes to the .js file. Accordingly, the frontendoa does not have these changes, since they work in more than one environment. In connection with these, I would like to know how to set up work between the frontend and backend.

Answer 1

Version control system?

Answer 2

The first and most important thing in the project is people. Do your back and front do not communicate with each other at all? They need to choose a tool with which they will synchronize their work.

Answer 3

git