Tips on how to remove a function from a union

type A = (() => void) | (() => number) | string

type B = Another<A> // string

Is there a way to remove all functions from type A?

This would result in type B being string

Answer №1

To filter out the Exclude types and keep only the strings, you can use the Exclude method along with the Function type:

type A = (() => void) | (() => number) | string

type B = Exclude<A, Function> // Only strings will remain

Answer №2

In my implementation, I followed a similar approach as suggested by @colinD, but with a slight modification. Instead of using the Function type, I utilized (...args: any[]) => any. This change was necessary because the usage of the Function type in eslint typescript led to issues.

Avoid using `Function` as a type declaration. The `Function` type can accept any function-like value, providing no guarantee of type safety during function calls. This lack of specificity can introduce bugs and errors into your code. Additionally, it can erroneously accept things like class declarations that will fail at runtime when not called correctly with `new`. If you expect certain arguments for the function, define the function shape explicitly instead.  @typescript-eslint/ban-types

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