env create react app code example

Example 1: new create react app

npx create-react-app my-app
cd my-app
npm start
//Note:npx on the first line is not a typo — 
//it’s a package runner tool that comes with npm 5.2+.

Example 2: create-react-app enviroment variables

process.env.NODE_ENV gives you either "development" or "production" or "test"
When you run npm start it is equal to develpment
When you run npm run build it is equal to production
When you run npm test it is equal to test