Node process.env.VARIABLE_NAME returning undefined

I got a problem just now , and I use this solved it in webpack config

const plugins = [
    new webpack.NoEmitOnErrorsPlugin(),
    // after compile global will defined `process.env` this Object
    new webpack.DefinePlugin({
      BUILD_AT : Date.now().toString(32),
      DEBUG: process.env.NODE_ENV !== 'production',
          'process.env': {
              'NODE_ENV': JSON.stringify(process.env.NODE_ENV || "development"),
              'VARIABLE_NAME': JSON.stringify(process.env.VARIABLE_NAME)
     }
   })
]

nodemon.json file is only for setting nodemon specific configuration So for create custom environment variables we can use dotenv package

First , Install dotenv package

npm install dotenv --save

after that create .env file in root and include environment variables as bellows

MONGO_ATLAS_PW=xxxxx
JWT_KEY=secret

Finally, inside your app.js file insert following after your imports.

require('dotenv').config()

Then you can use environment varibale like this

process.env.MONGO_ATLAS_PW
process.env.JWT_KEY

process.env.VARIABLE_NAME returns undefined because the Node.js execution environment does not know the newly added VARIABLE_NAME yet. To fix the issue, the Node.js execution environment (e.g. IDE) need to restart.

The following steps can be used to reproduce this issue:

1. Open IDE such as WebStorm and write a simple Node.js program: console.log(process.env.VARIABLE_NAME). It will print undefined as expected, as VARIABLE_NAME is not defined yet. Keep the IDE running, don't close it.
2. Open environment profile such as .bash_profile and add export VARIABLE_NAME=mySensitiveInfo in it.
3. Open system console and run source .bash_profile, so that the above export statement will be executed. From now on, whenever system console is opened, VARIABLE_NAME environment variable exists.
4. In system console, execute the Node.js program in step 1, it will print mySensitiveInfo.
5. Switch to IDE and execute Node.js program, it will print undefined.
6. Restart the IDE and execute Node.js program, this time, it will print mySensitiveInfo