How can I set an environmental variable in node.js?

You can set your environment variables in process.env:

process.env['VARIABLE'] = 'value';

-OR-

process.env.VARIABLE = 'value';

Node should take care of the platform specifics.

First you should install this package :- https://github.com/motdotla/dotenv [npm install dotenv]

Then you need to create a .env file in your project's root directory, and there you can add variables like below:-

NODE_ENV=PRODUCTION
DATABASE_HOST=localhost

Now you can easily access these variables in your code like below:-

require('dotenv').config()
console.log(process.env.NODE_ENV);

It worked for me, hopefully that helps.