How to correctly use dotenv / .env for passing parameters in typescript?

January 12, 2023

I’ve got a typescript app that I’m editing via VS Code. I’ve removed sensitive information into a .env file:

# .env file
NAME='foobar'

In my main app, that is consuming the .env file, I have installed the dotenv npm package. I’m also trying to pass the environment variable as parameter to a function in another file.

App.ts

import {
    printName
} from "./printStuff"
import * as dotenv from 'dotenv'
dotenv.config()

await printName(process.env.NAME)

printStuff.ts

export async function printName(name: string){
    console.log(name)
}

This is where the issue occurs. I get the dreaded red squiggly lines under process.env.NAME in the app.ts

string | undefined
Argument of type 'string | undefined' is not assignable to parameter of type     'string'.
  Type 'undefined' is not assignable to type 'string'.ts(2345)

I’ve been able to solve this via

    await printName(process.env.NAME || '')

but this seems off to me. Is there a better way of doing this?
My apologies in advance, I’m new to Typescript.

>Solution :

Using a non-null assertion operator:

await printName(process.env.NAME!); // ok

but keep in mind this is just an assertion for TypeScript to tell it that it isn’t undefined. It can still be undefined at runtime if you don’t set the env variable and can cause issues.