TypeScript comes with built-in utility types that help us transform and work with types more effectively. Here’s a quick and beginner-friendly guide to five of the most commonly used ones.
Record<Keys, Type>
What it does: Creates an object type with specific keys, and all values having the same type.
type UserRole = "admin" | "editor" | "viewer";
const roles: Record<UserRole, boolean> = {
admin: true,
editor: false,
viewer: true,
};
Think of it as: An object where every key is required and the values all follow a single type.
Omit<Type, Keys>
What it does: Removes specific keys from a type.
type User = {
id: string;
name: string;
email: string;
};
type PublicUser = Omit<User, "email">;
Result: PublicUser will have only id and name.
Pick<Type, Keys>
What it does: Selects specific keys from a type.
type User = {
id: string;
name: string;
email: string;
};
type UserPreview = Pick<User, "name" | "email">;
Result: UserPreview will only include name and email.
Partial<Type>
What it does: Makes all properties optional.
type User = {
id: string;
name: string;
};
type UpdateUser = Partial<User>;
Result: UpdateUser can be {}, { id: "123" }, or { name: "John" }.
Extract<Type, Union>
What it does: Extracts only the types that are shared between two unions.
type Roles = "admin" | "editor" | "user";
type AllowedRoles = Extract<Roles, "admin" | "user">;
Result: AllowedRoles will be 'admin' | 'user'.
Summary
| Utility | What it does |
| --------- | ------------------------------------------------ |
| `Record` | Create an object with fixed keys and value types |
| `Omit` | Remove keys from a type |
| `Pick` | Select only specific keys from a type |
| `Partial` | Make all fields optional |
| `Extract` | Keep only matching values from a union |Tip: These utilities are great for building reusable, flexible types. They're simple but powerful once you get the hang of them!