yarn start add variable code example

Example: react environment variables

// Place a filer called .env at the doc root of your project
/*
my-react-app/ 
 |-node-modules/
 |-src/
 |-public/
 |-.env
 |-gitignore
 |-package.json
 |-package.lock.json.
 |-README.md
*/
// Edit the .env file and create your cusotm Environment Variables
// DO NOT USE SINGLE OR DOUBLE QUOTES!

REACT_APP_CLIENT_ID=jfjffffaddfeettgydgdffv
REACT_APP_KEY=aaddddawrfffvvvvssaa

// They will be READ-ONLY from your JS file, you can print them
// or assign them to other variables

console.log(process.env.REACT_APP_CLIENT_ID);
console.log(process.env.REACT_APP_KEY);

var id = process.env.REACT_APP_CLIENT_ID;
var key = process.env.REACT_APP_KEY;