How to convert a named tuple to a unnamed tuple in TypeScript 4.0?

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Since TypeScript 4.0, we have named tuples, which is great:

type Fn = (foo: number) => void;

type Foo = Parameters<Fn>;
// type Foo = [foo: number];

However, I am facing a situation in which I now have a named tuple but the names are just clutter. I don't want the names.

How can I build a RemoveNames<T> utility type that will take [foo: number] and return [number]?

Note: of course, I need it to work with tuples of any size.

typescript tuples
1 Answers

Those tuple names tend to be pretty sticky, but they do disappear if you prepend/append a non-named element to the tuple. So one way to do this could be to prepend and then remove some type, like this:

type RemoveNames<T extends any[]> = [any, ...T] extends [any, ...infer U] ? U : never

That seems to act the way you want:

type UnnamedFoo = RemoveNames<Foo>;
// type UnnamedFoo = [number]

Playground link to code

user_28872180
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