Toggle between multiple .env files like .env.development with node.js

For TypeScript / ESM:

import dotenv from 'dotenv'

dotenv.config({ path: `.env.${process.env.NODE_ENV}` })

The above two answers are both slightly off. let me explain. Answer from KyleMit below is missing ./ to indicate current directory.

• the ./ indicates current directory in Node.js. The Second . prior to env indicates a hidden/private file. Thats why in KyleMits answer if the env file was not in the root of the PC it would never find it. The simplest way to do it in my opinion is to add a ./ this says "hey computer look in my current directory for this file".

//look in my current directory for this  hidden file. 
// List hidden files in dir: ls -a
 
require('dotenv').config({ path: `./.env.${process.env.NODE_ENV}` })


//I reccomend doing a console.log as well to make sure the names match*
console.log(`./.env.${process.env.NODE_ENV}`)

I'm using the custom-env npm package to handle multiple .env files. Just put this at the top of your code:

require('custom-env').env();

and it will load environment variables from the file .env.X, where X is the value of you NODE_ENV environment variable. For example: .env.test or .env.production.

Here is a nice tutorial on how to use the package.

From answers from above: This is the final result that worked for me.

.env.dev file in src dir.

import path from 'path';

dotenv.config({ path: path.join(__dirname, `./.env.${process.env.NODE_ENV}`)});

This work for me:

File .env

NODE_ENV=dev
DB_HOST=localhost

File .env.dev

DB_HOST=dev-host
DEV_VAR=new-variable

Code

require("dotenv").config();

if (process.env.NODE_ENV === "dev") {
  const result = require("dotenv").config({ path: ".env.dev" });

  process.env = {
    ...process.env,
    ...result.parsed,
  };
}

const dbConfig = {
  host: process.env.DB_HOST,
};

console.log(dbConfig.host);
console.log(process.env.DEV_VAR);

Update:

Note that Node.js has had built-in support for envs after 20.6.0.

Install the dotenv package:

npm install dotenv

We need to get the .env file name based on NODE_ENV, it might be undefined, set default to development:

const envFileName = `.env.${process.env.NODE_ENV || "development"}`

Import the dotenv package and use it:

dotenv.config({ path: envFileName });

You can try: https://www.npmjs.com/package/dotenv-cli, use it like this:

"scripts": {
    "start": "dotenv -e .env.development node ./bin/www",
    "start-prod": "dotenv -e .env.production node ./bin/www"
}

package.json

"scripts": {
    "start-dev": "dotenv_config_path=.env.development nodemon index.js",
    "start-prod": "dotenv_config_path=.env.production nodemon index.js"
  },

If you want to have default environment variables too:

dotenv.config(); // Loads the default .env.
dotenv.config({ path: `.env.${process.env.NODE_ENV}` }); // loads the environment specific .env if any.

Step 1: create a .env.dev file in the root director

Step 2: add this code in ur app.js or db.js

dotenv.config({ path: ['.env.dev', '.env'] }); // for development

dotenv.config(); // for production

Step 3: Restart the Server

I am using Node.js v22.1.0 and Express 4.16.1 and Dotenv ^16.4.5

I wish to publish my own answer to provide additional practical infos.
In the following example I will show a slightly different multi-env handling.

Needed files (it is not a law)

• .env --> for common variables
• .env.production --> for production only variables
• .env.development --> for development only variables

Import the envs

First of all import the common one.

require('dotenv').config({ path: '.env' });

Then import the one that depends on the running mode

require('dotenv').config({ path: `.env.${process.env.NODE_ENV}` });

Note
This one will skip eventual variables declared by the previous env import (in our case, the common one).

Where the NODE_ENV comes from?

I personally use the VSC Nodejs debugger functionality, so I needed to setup it too.

package.json

  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "dev": "NODE_ENV=development nodemon src/server.js",
    "start": "NODE_ENV=production node src/server.js"
  },

launch.json

This piece was generated by VSC by clicking on "create launch.json file" in the Debug section, and then selecting NodeJs.

{
    "version": "0.2.0",
    "configurations": [
        {
            "type": "node",
            "request": "launch",
            "name": "Launch Program",
            "skipFiles": [
                "<node_internals>/**"
            ],
            "program": "${workspaceFolder}/src/server.js",
            "env": {
                "NODE_ENV": "development"
            }
        }
    ]
}

Hope this helps. Bye.