Typescript - How to selection the overload function signature to get parameters types from? [duplicate]

Question

Let's say a simple overloaded function defined as the following:

function f(p: number) : string;
function f(p: string) : undefined;

function f(p: number | string): number | string {
    return (typeof p === 'number') ? String(p) : undefined;
}

Parameters<typeof f>[0] gives me only string. Because it's the last overload defined.

How to choose which overload function to get the parameters from ?
Without having to reorder the definitions of course.

Do's and Don'ts States to use Union types instead of duplicate overloads differing by param types — Andrew Nolan
– Andrew Nolan, Commented Jan 31, 2020 at 13:30
@AndrewNolan It also states Note that we didn’t make b optional here because the return types of the signatures differ. Like so, since mines have differents returns types, this is not a problem at all. — Yairopro
– Yairopro, Commented Jan 31, 2020 at 13:37

Roberto Zvjerković · Accepted Answer · 2020-01-31 13:54:13Z

0

Maybe rather use a generic function?

function f<K extends number | string>(p: K): K {
    return p;
}

answered Jan 31, 2020 at 13:54

Roberto Zvjerković

10.2k4 gold badges31 silver badges49 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Yairopro Over a year ago

No. The snippet I used was just to simplify the exemple. I updated

Collectives™ on Stack Overflow

Typescript - How to selection the overload function signature to get parameters types from? [duplicate]

1 Answer 1

1 Comment

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Linked

Related