How to tell TypeScript my function argument is an Enum key?

Question

I have an enum thats maps HTTP status to their code, as follow:

I can easily get those codes by accessing their keys (notice how IntelliSense shows HttpStatus.NOT_FOUND = 404 on the right panel)

Now let's say I have a function called sendStatus:

How should I type this function in order to get those codes autocompleted by IntelliSense?

Using keyof typeof doesn't work because it doesn't autocomplete the enum values.

Answer 1

What you want is not directly possible. When you do keyof typeof you create a union type 'CREATED' | 'OK' | 'NOT_FOUND' ... that is completely separate from the enum it once was.

The closest you can get is by doing

function sendStatus(code: HttpStatus) {
    // code
}

send(HttpStatus.OK) // This will autocomplete and show the status code numbers

and then converting the code to string inside the sendStatus function.

It's hard to say what you really want without knowing the exact usage you're looking for, but I would consider just having a plain old object instead of the enum

const HTTP_STATUS = {'OK':200, 'CREATED':201} as const

Then, if you need to, you can also create both of the types like so

type StringStatus = keyof typeof HTTP_STATUS // 'OK' | 'CREATED'
type NumsStatus = (typeof HTTP_STATUS)[keyof typeof HTTP_STATUS] // 200 | 201

Generally there's rarely a good reason to use enums in modern TS. Usually objects and/or union types do the job much better.