How to manage environment variables in Node.js

Environment variables are named values that can be used to configure applications and processes, allowing for easy customization and portability. They provide a way to store and manage configurations, such as API keys, database credentials, and other settings, outside of your code.

In Node.js, you can access these variables throughout your application code using the process.env property, which is a global object that holds all environment variables as key-value pairs.

There are several ways to set and use environment variables in Node.js, depending on your needs and preferences. Some of the common methods are:

Using the dotenv package

This is a popular and easy way to load environment variables from a .env file into the process.env object. You can install the package using npm install dotenv, and then create a .env file in your project’s root directory, where you can add variables like this:

NODE_ENV=production
DATABASE_HOST=localhost

Then, you can load the .env file in your Node.js project by requiring the dotenv package at the top of your entry point file, like this:

require('dotenv').config();

This will make the variables available in the process.env object, and you can access them like this:

console.log(process.env.NODE_ENV); // 'production'
console.log(process.env.DATABASE_HOST); // 'localhost'

Using the command line

You can also set environment variables directly from the command line when you run your Node.js application. For example, you can use the set keyword on Windows or the export keyword on Linux or Mac to set a variable, like this:

export NODE_ENV=production

Then, you can run your Node.js application with the variable set, like this:

node app.js

You can also set multiple variables in one line by separating them with a space, like this:

export NODE_ENV=production DATABASE_HOST=localhost

You can access the variables in the same way as before, using the process.env object. However, note that these variables are only available for the current session, and they will not persist if you close the terminal or switch to another session.

Using the npm scripts

Another way to set and use environment variables in Node.js is to use the npm scripts in your package.json file. This allows you to define different scripts for different environments, and set the variables accordingly. For example, you can have a script for development and a script for production, like this:

"scripts": {
  "start": "node app.js",
  "start:dev": "NODE_ENV=development node app.js",
  "start:prod": "NODE_ENV=production node app.js"
}

Then, you can run the appropriate script depending on the environment you want to use, like this:

npm run start:dev
npm run start:prod

You can access the variables in the same way as before, using the process.env object.