Using environment variables in the .env file in reactjs

.env file

REACT_APP_NODE_ENV=

REACT_APP_GOOGLE_KEY=

index.js

import dotenv from "dotenv";

dotenv.config();

...

const { REACT_APP_NODE_ENV, REACT_APP_GOOGLE_KEY } = process.env;

...

You can use dotenv module with REACT_APP_ prefix..