Node.js unset environment variable

Question

How do you unset an environment variable in Node.js?

I've tried:

process.env.MYVAR = undefined

But that doesn't unset it, it appears as follows:

console.log('xx' + process.env.MYVAR + 'xx');

Output is:

xxundefinedxx

I want:

xxxx

How do I make this work?

Answer 1

There is another unintuitive aspect to it: Node.js converts undefined to the string "undefined" when assigning an environment variable:

> process.env.MYVAR = undefined
undefined
> typeof process.env.MYVAR
'string'

You can work around this using delete:

> delete process.env.MYVAR
true
> typeof process.env.MYVAR
'undefined'

Tested with Node.js 13.5, 12.14 and 10.18.

For this reason (process.env.MYVAR || '') does not help, as it evaluates to ('undefined' || '').