When developing the React app with back-end API, we often need to define environment variables for different environments. For example, in my project, I have two environments: test and prod, which are connected to different serverless backend. This is to make sure that the developer can work in an environment that is isolated from the production environment.

Suppose we are going to deploy our React app to the testing and production server using test and prod environment variables and we do not want to eject the project.

Create Environment Variable Files

Create files called .env.test and .env.prod at the root of your project.

Set environment variables in .env.test and .env.prod files.

For example, in the .env.test we have REACT_APP_API_URL=http://api-test.example.com, in the .env.prod we have REACT_APP_API_URL=http://api.example.com.

According to the Create React App document, we must create custom environment variables beginning with REACT_APP_.

Install env-cmd

This is a simple node program for executing commands using an environment from an env file.

$ npm install env-cmd --save

Update scripts

Add some new scripts to your package.json.

  "scripts": {
    "build:test": "env-cmd -f .env.test npm run build"
    "build:prod": "env-cmd -f .env.prod npm run build"


for example:

var url = process.env.REACT_APP_API_URL + '/sms?key=' + this.state.currentFileName;


# build for test server
$ npm run build:test

# build for prod server
$ npm run build:prod

Categories: Development