Just started doing some react js for fun and was wondering if anyone had any good content or git projects on it. I mainly need help with trying to make REST API calls. i have a backend in express/mongo db and want to connect the frontend to the backend with get/post/put calls. Been searching online and cant find anything useful.

Use one of the many libraries for that like jquery or you could use the built in fetch command. ReactJS probably doesn't have anything built in because that isn't the point of react.