How can I check if an environment variable is set in Node.js?

I would like to check if an environment variable is set in my Express JS server and perform different operations depending on whether or not it is set.

I've tried this:

if(process.env.MYKEY !== 'undefined'){
    console.log('It is set!');
} else {
    console.log('No set!');
}

I'm testing without the process.env.MYKEY but the console prints "It is set".

This is working fine in my Node.js project:

if(process.env.MYKEY) { 
    console.log('It is set!'); 
}
else { 
    console.log('No set!'); 
}

---

EDIT:

Note that, As @Salketer mentioned, depends on the needs, falsy value will be considered as false in snippet above. In case a falsy value is considered as valid value. Use hasOwnProperty or checking the value once again inside the block.

> x = {a: ''}
{ a: '' }
> x.hasOwnProperty('a')
true

Or, feel free to use the in operator

if ("MYKEY" in process.env) {
    console.log('It is set!');
} else {
    console.log('No set!');
}

I use this snippet to find out whether the environment variable is set

if ('DEBUG' in process.env) {
  console.log("Env var is set:", process.env.DEBUG)
} else {
  console.log("Env var IS NOT SET")
}

---

Theoretical Notes

As mentioned in the NodeJS 8 docs:

> The process.env property returns an object containing the user environment. See environ(7). > > [...] > > Assigning a property on process.env will implicitly convert the value to a string. > > > > process.env.test = null > console.log(process.env.test); > // => 'null' > process.env.test = undefined; > console.log(process.env.test); > // => 'undefined'

Though, when the variable isn't set in the environment, the appropriate key is not present in the process.env object at all and the corresponding property of the process.env is undefined.

Here is another one example (be aware of quotes used in the example):

console.log(process.env.asdf, typeof process.env.asdf)
// => undefined 'undefined'
console.log('asdf' in process.env)
// => false

// after touching (getting the value) the undefined var 
// is still not present:
console.log(process.env.asdf)
// => undefined

// let's set the value of the env-variable
process.env.asdf = undefined
console.log(process.env.asdf)
// => 'undefined'

process.env.asdf = 123
console.log(process.env.asdf)
// => '123'

A side-note about the code style

I moved this awkward and weird part of the answer away from StackOverflow: it is here

Why not check whether the key exists in the environment variables?

if ('MYKEY' in Object.keys(process.env))
    console.log("It is set!");
else
    console.log("Not set!");

As the value (if exist) will be a string, as mentioned in the documentation:

process.env.test = null;
console.log(process.env.test);
// => 'null'
process.env.test = undefined;
console.log(process.env.test);
// => 'undefined'

and empty string can be returned (that happened to me in CI process + GCP server),

I would create a function to clean the values from process.env:

function clean(value) {
  const FALSY_VALUES = ['', 'null', 'false', 'undefined'];
  if (!value || FALSY_VALUES.includes(value)) {
    return undefined;
  }
  return value;
}

const env = {
  isProduction: proces.env.NODE_ENV === 'production',
  isTest: proces.env.NODE_ENV === 'test',
  isDev: proces.env.NODE_ENV === 'development',
  MYKEY: clean(process.env.MYKEY),
};
 
// Read an environment variable, which is validated and cleaned
env.MYKEY           // -> 'custom values'
 
// Some shortcuts (boolean) properties for checking its value:
env.isProduction    // true if NODE_ENV === 'production'
env.isTest          // true if NODE_ENV === 'test'
env.isDev           // true if NODE_ENV === 'development'

EDIT (removed old incorrect answer)

As maxkoryukov said, it should be:

# in test.js

if ("TEST_ENV" in process.env) {
    console.log("TRUE: " + process.env["TEST_ENV"])
} else {
    console.log("FALSE")
}

This was true with he following test:

$> node test.js
FALSE
$> export TEST_ENV="SOMETHING"
$> node test.js
TRUE: SOMETHING

This also works when the variable is an empty string (tested in a new bash session/terminal window).

$> node test.js
FALSE
$> export TEST_ENV=""
$> node test.js
TRUE:

If you're assigning a value with your if statement, you could do it like this

var thisIsSet = 'asddas';
var newVariable = thisIsSet ||'otherValue'
console.log(newVariable)

Results in asddas

I do practice to use built-in Node.js assert library.

const assert = require('assert');

assert(process.env.MY_VARIABLE, 'MY_VARIABLE is missing');
// or if you need to check some value
assert(process.env.MY_VARIABLE.length > 1, 'MY_VARIABLE should have length greater then 1');

I use to add this validation on top of the index.js, and keep it up to date with the code requirements. This way is also easy to check which variables are required for the project, if for some reason .env.example is not in the code.

It's good way to check your environment variable

if (process.env.YOUR_ VARIABLE) {
    // If your variable is exist
}

Otherwise, If you would like to check multiple environment variables, you can check this node module out.

node-envchecker

You can create .env.example which stores all the required env variable by the application.
After this you can load this .env.example and compare with .env.

In this way, you can check all the required envs on the time of application start.

To minimize the task, you can use scan-env npm package, which does the same.

const scanEnv = require("scan-env");

const scanResult = scanEnv();

if (!scanResult) {
  console.error("Environment variables are missing.");
}

tutorial to use scan-env

You can solve easily with || operator with default value attribution case the env var doesn't exist:

const mykey = process.env.MYKEY || '1234';

let dotenv;

try {
  dotenv = require('dotenv');
  dotenv.config();
}
catch(err) {
  console.log(err);
  // if vars are not available...
}

//... vars should be available at this point