This is a very common thing now a days to face the requirements as a full stack web developers that we asked to integrate a REST API with React front end which is most popular javascript front end framework now a days.
In this work sample I have mentioned how you can create a React front end application and integrate this with a REST api. For REST api here I have used Rails api only application, how ever you can use any backend REST api here the basic will be same. You just need to make some changes into URL based upon which back end you are using.
You need to run clone both applications i.e. the React front end app and the Rails API app.
Here I am sharing url for both application.
React Front End App: https://github.com/RaviSys/rails-api-integration-with-react
Rails Back End App: https://github.com/RaviSys/rest-api-for-react
Checkout the working demo here