reactjs - How to use diferent .env files with nextjs?

Question

I would like to have different configuration files for the environment variables and be able to use them in my next project. I saw the example with dotenv.

But I don't like to define the variables in the .env file and also define them in the config.next.js file. if for some reason I put the variables in the .env file but forget to put them in the config.next.js file the code starts having problems. Theres is a way to do it more eficiently?

My scripts in package.json:

"scripts": {
    "dev": "next",
    "build": "next build",
    "start": "next start",
    "lint": "eslint pages --ext .ts,.tsx,.js",
    "test": "jest",
    "commit": "git-cz",
    "dev:production": "dotenv next"
},

My .env vars

TITULO=react, typescript, material ui App

Component

import { NextPage }          from 'next';
import { FunctionComponent } from 'react';

interface HelloWorldProps {
  nombre: string,
  saludo?: string
}


const HelloWorld: FunctionComponent<HelloWorldProps> = ({ nombre, saludo = 'noches' }: HelloWorldProps) => (
  <>
    <h1>Hola {nombre} buenas {saludo}</h1>
    {/* eslint-disable-next-line multiline-ternary */}
    <h2>{process.env.TITULO ? 'hola' : 'adios'}</h2>
  </>
);

const Home: NextPage = () => <HelloWorld nombre="cristian" />;

export default Home;

Answer 1

Next 9.4 has built-in support for .env files: https://nextjs.org/docs/basic-features/environment-variables

But, in case you want to have multiple .env files, like:

• .env.development
• .env.staging
• .env.prestaging
• .env.production

It would be impossible to do with a built-in env variables support. There's only 3 environments that officially supported for now, it's: "development", "test", "production". With next dev you use "development", next build && next start uses "production" environment.

If you need to build for production environment, but using ".env.staging" for example, then you need to add env-cmd package, and add this line to your package.json:

"build:staging": "env-cmd -f .env.staging yarn build && yarn start"

Next would make a production build with ".env.staging" variables.