How can function overloads with varying arities be refactored without resorting to the use of over

In my typescript function declaration, I have specified different arity settings:

function f(): void;
function f(code: 0): void;
function f(code: 1, msg: string): void;
function f(code: 0 | 1 = 0, msg?: string): void { /* omit implementation */ }

This allows the function to be called in various ways:

f() // valid
f(0) // valid
f(1, "error message") // valid
f(0, "message") // type error
f(1) // type error

I am interested in refactoring this function declaration without relying on function overloads. Are there alternative methods such as using union types or conditional types to achieve this?

Answer №1

Learn how to use union types for typing argument combinations:

function f(...args: [] | [0] | [1, string]): void { /* implementation omitted */ }

Check out the Playground here

* The version with overloads is still considered cleaner in terms of readability.

Answer №2

What do you think of this code snippet?

type Post = {id: 1} | {id: 2, postText?: string};

const usePost = (post?: Post) => {};

const usedPost_0 = usePost();
const usedPost_1 = usePost({id: 1});
const usedPost_2 = usePost({id: 2});

const usedPost_3 = usePost({id: 1, postText: 'something'}); // type error
const usedPost_4 = usePost({id: 2, postText: 'something'});

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