Ensuring accurate validation of function arguments in Typescript

Question

Ensuring accurate validation of function arguments in Typescript

Today is my second day diving into the world of typescript and I find myself puzzled by a particular situation:

Let's imagine we have a file named .env which contains a variable called ACCESS_TOKEN_SECRET

ACCESS_TOKEN_SECRET = 9i0d98f7a0sd87fy03eihdq2iudh...

We may need to pass this variable to a function in our TypeScript code, like so:

const accessToken = jwt.sign(user, process.env.ACCESS_TOKEN_SECRET)

At this stage, our IDE might flag up an issue stating that the process.env.ACCESS_TOKEN_SECRET variable may not be a string

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

To address this, I decided to check if the process variable is indeed a string

if(typeof process.env.ACCESS_TOKEN_SECRET !== 'string') throw new Error()
const accessToken = jwt.sign(user, process.env.ACCESS_TOKEN_SECRET)

However, I still feel somewhat uncertain about this solution. Is this really the correct way TypeScript expects me to tackle this issue?

typescript types jwt

Answer 1

Answer №1

Absolutely. That method is definitely a valid approach to tackling this scenario.

Alternatively, you could simply verify for the presence of undefined since TypeScript considers it sufficient to narrow down the type. Here's an example:

if (process.env.ACCESS_TOKEN_SECRET) {
  const accessToken = jwt.sign(user, process.env.ACCESS_TOKEN_SECRET)
}

Another option is to terminate early:

if (process.env.ACCESS_TOKEN_SECRET === undefined) {
  return; //or throw an error
}

Answer 2

Absolutely. That method is definitely a valid approach to tackling this scenario.

Alternatively, you could simply verify for the presence of undefined since TypeScript considers it sufficient to narrow down the type. Here's an example:

if (process.env.ACCESS_TOKEN_SECRET) {
  const accessToken = jwt.sign(user, process.env.ACCESS_TOKEN_SECRET)
}

Another option is to terminate early:

if (process.env.ACCESS_TOKEN_SECRET === undefined) {
  return; //or throw an error
}

Ensuring accurate validation of function arguments in Typescript

Answer №1

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