(1) TypeScript: Create Optional Types From Old Types?

#webdev #beginners #javascript #tutorial

Here's a quick tip on how to use already-existing types to create a new type with optional properties without changing the original type:

type ToptionalProps<T> = { [K in keyof T]?: T[K] };

// Example Interface:

interface Tuser {
  id: number;
  name: string;
  email: string;
}

type ToptionalUser = ToptionalProps<Tuser>;

// Equivalent to: type ToptionalUser = { id?: number; name?: string; email?: string };

// ==== And you can play around and Pick and Omit like so: =====

type TnameAndIdUser = Omit<Tuser, "email">
type TomittedOptionalProps<T> = { [K in keyof T]?: T[K] };

type ToptionalUser2 = TomittedOptionalProps<TnameAndIdUser>;

const newUser: ToptionalUser2 = {email: "newuser@gmail.com"}
// Error 'email' does not exist in type 'TpickedOptionalProps<x>';