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

Question

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".

Answer 1

This is working fine in my Node.js project:

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

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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!'); } 

Answer 2

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") } 

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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