Putting .env variables in for command not session

I have a .env file with variables in it like this:

HELLO=world
SOMETHING=nothing

I found this awesome script the other day, that puts these variables into the current session so when I run something like this

$(cat ./.env | grep -v ^# | xargs) && node test

Then I can access the variables in the test.js node file.

console.log(process.env.HELLO)
console.log(process.env.SOMETHING)

The problem with this is that that command puts the .env variables in the entire session so when I run node test without $(cat ./.env | grep -v ^# | xargs) after I run it, it will still have access to those variables, I'm writing a node.js test that accounts for these variables and I'd love to be able to run the same command with and without these .env variables without worrying if they are still in the session. Ideally I want to run

put-env-variables-for-this-command-first-command node test && node test

And have the env variables only be available in the test script the first time it runs.