Skip to content
BSWEN
Blog

How to set environment variable when using 'npm' command in node.js applications?

Cowrie
Cowrie
Dev @ Bswen

1. Purpose

In this post, I will demonstrate how to set environment variables for npm commands, I need to execute the following command to export an environment variable before running npm start:

Terminal window
export NODE_OPTIONS=--openssl-legacy-provider

Then I would run:

Terminal window
npm start

However, it is tedious to execute the export command every time I start the application. For example:

Terminal window
export NODE_OPTIONS=--openssl-legacy-provider
npm start


....
export NODE_OPTIONS=--openssl-legacy-provider
npm start


....
export NODE_OPTIONS=--openssl-legacy-provider
npm start

Is there a way to set this up just once?

Yes, you can achieve this by using cross-env in your package.json.

2. The solution

2.1 The answer

TL;DR: The solution is to modify your package.json file.

Before:

package.json
"start": "react-scripts start",

After modification:

package.json
"start": "cross-env NODE_OPTIONS=--openssl-legacy-provider react-scripts start",

The key difference is the addition of a prefix to the original command:

cross-env NODE_OPTIONS=--openssl-legacy-provider

Now, you can start the application with:

Terminal window
➜  my-app git:(master) ✗ npm start


> [email protected] start
> cross-env NODE_OPTIONS=--openssl-legacy-provider react-scripts start


Compiled successfully!


You can now view my-app in the browser.


  Local:            http://localhost:3000


Note that the development build is not optimized.
To create a production build, use npm run build.

With this setup, you no longer need to manually set the NODE_OPTIONS environment variable each time you start the app. Simply configure it in your package.json, and you’re done.

2.2 The theory

1) What is cross-env?

The core module used to resolve this issue is cross-env. But what exactly is cross-env?

cross-env allows you to set environment variables in a way that works across different platforms. You can define environment variables as you would on a POSIX system, and cross-env ensures they are set correctly regardless of the platform.

2) How to install cross-env?

You can install cross-env globally using the following command:

Terminal window
npm install -g cross-env

Version 7 of cross-env only supports Node.js 10 and higher. If you are using Node.js 8 or lower, install version 6:

Terminal window
npm install -g cross-env@6

3) How to use cross-env?

Here are some examples of how to use cross-env:

package.json
{
  "scripts": {
    "build": "cross-env NODE_ENV=production webpack --config build/webpack.config.js"
  }
}

You can also set multiple environment variables:

package.json
{
  "scripts": {
    "start": "cross-env FIRST_ENV=one SECOND_ENV=two node ./my-program"
  }
}

Additionally, you can split a command into multiple lines or separate the environment variables declaration from the actual command execution:

package.json
{
  "scripts": {
    "parentScript": "cross-env FIRST_ENV=\"one\" npm run childScript",
    "childScript": "cross-env-shell \"echo Hello $FIRST_ENV\""
  }
}

3. Summary

In this post, I demonstrated how to set environment variables for your Node.js applications using the cross-env tool. This approach eliminates the need to manually export variables each time you run your application. By configuring your package.json file, you can streamline your development workflow and ensure consistent behavior across different platforms.

Final Words + More Resources

My intention with this article was to help others who might be considering solving such a problem. So I hope that’s been the case here. If you still have any questions, don’t hesitate to ask me by email: Email me

Here are also the most important links from this article along with some further resources that will help you in this scope:

Oh, and if you found these resources useful, don’t forget to support me by starring the repo on GitHub!

Tags: