Why is process.env.NODE_ENV undefined?

Question

process.env is a reference to your environment, so you have to set the variable there.

To set an environment variable in Windows:

SET NODE_ENV=development

on macOS / OS X or Linux:

export NODE_ENV=development

tips

in package.json:

"scripts": {
  "start": "set NODE_ENV=dev && node app.js"
 }

in app.js:

console.log(process.env.NODE_ENV) // dev
console.log(process.env.NODE_ENV === 'dev') // false
console.log(process.env.NODE_ENV.length) // 4 (including a space at the end) 

so, this may better:

"start": "set NODE_ENV=dev&& node app.js"

or

console.log(process.env.NODE_ENV.trim() === 'dev') // true

For people using *nix (Linux, OS X, etc.), there's no reason to do it via a second export command, you can chain it as part of the invoking command:

NODE_ENV=development node server.js

Easier, no? :)

We ran into this problem when working with node on Windows.

Rather than requiring anyone who attempts to run the app to set these variables, we provided a fallback within the application.

var environment = process.env.NODE_ENV || 'development';

In a production environment, we would define it per the usual methods (SET/export).

You can use the cross-env npm package. It will take care of trimming the environment variable, and will also make sure it works across different platforms.

In the project root, run:

npm install cross-env

Then in your package.json, under scripts, add:

"start": "cross-env NODE_ENV=dev node your-app-name.js"

Then in your terminal, at the project root, start your app by running:

npm start

The environment variable will then be available in your app as process.env.NODE_ENV, so you could do something like:

if (process.env.NODE_ENV === 'dev') {
  // Your dev-only logic goes here
}

In macOS for those who are using the express version 4.x.x and using the DOTENV plugin, need to use like this:

1. After installing the plugin import like the following in the file where you init the application: require('dotenv').config({path: path.resolve(__dirname+'/.env')});

2. In the root directory create a file '.env' and add the varaiable like:

   NODE_ENV=development or NODE_ENV = development

in package.json we have to config like below (works in Linux and Mac OS)

the important thing is "export NODE_ENV=production" after your build commands below is an example:

  "scripts": {
     "start": "export NODE_ENV=production && npm run build && npm run start-server",
     "dev": "export NODE_ENV=dev && npm run build && npm run start-server",
  } 

• for dev environment, we have to hit "npm run dev" command

• for a production environment, we have to hit "npm run start" command