How to define environment variable in create-react-app?

Environment Variable works differently in create-react-app. To access the environment variable in your app, you have to add the prefix REACT_APP_ before defining your variable as described in the below image.

create-react-app-env

In our app, you can access this variable as a process.env variable.

let BACKENDURL = process.env.REACT_APP_BACKENDURL || "http://localhost:8080";

You can define the environment variable in the .env file. If you are hosting your app in production like Netlify or Heroku, you can define varibles in their dashboard.