Env:
typescript 4.5.5
Errors
This expression is not callable.
Each member of the union type '{ <S extends User>(predicate: (this: void, value: User, index: number, obj: User[]) => value is S, thisArg?: any): S | undefined; (predicate: (value: User, index: number, obj: User[]) => unknown, thisArg?: any): User | undefined; } | { ...; }' has signatures, but none of those signatures are compatible with each other.ts(2349)
Error Screenshot
Currently, the users definition states it is either Array of User or Array of string.
You can change the definition to const users: Array<User | string> = res.data;.
This way while looping will be aware that the element inside an array can be both User or string.
Or if in your case you are sure that the users array can either be an array of User or string but not both, then you can keep the definition of users: User[] | string[], but trick Typescript while .find like (users as Array<User | string>).find((x: User | string) => {// find logic})
type Ugh<T> = (T extends (infer X)[] ? X : never)[]. Then, you can do something like (users as Ugh<typeof users>).find(...). 🤦 just rename Ugh in your actual code…