I have a Foo type that consists of multiple types
For example:
type Foo = string | number
I need to receive this type and convert it into an array of the individual types within the union
type TransformedFoo = ToUnionOfArray<Foo> // => string[] | number[]
Simply using Foo[] won't work in this case, since it would result in (string | number)[].
What's the best way to turn a union type into an array of its constituent types?
To leverage distributive conditional types, you can utilize the following syntax:
type Bar = boolean | number;
type Lists<U> = U extends any ? U[] : never;
type ModifiedBar = Lists<Bar>; // boolean[] | number[]
Conditional types turn into distributive forms when operating on a generic type within a union
To handle this situation, you can utilize distributive conditionals like so:
type ConvertToUnion<T> = T extends infer U ? U[] : never;
When the type parameter T is used in a conditional statement without any constraints, the conditional will be applied (or distributed) to each value within the input union T.
For more information on how this concept operates, check out this resource: Typescript Distributive Conditional Types
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