Utility Types

TypeScript provides several massively powerful globally scoped global mapping Utility Types! These utilities magically manipulate existing Types cleanly into brand new structural configurations natively!

1. Partial<T>

Maps all required properties inside a given Type completely as Optional (?). Incredibly useful for backend PATCH (Update) endpoints dynamically!

interface Todo {
    title: string;
    description: string;
}

// To update a Todo, we might only send the description.
function updateTodo(id: number, fieldsToUpdate: Partial<Todo>) {
    // fieldsToUpdate legally accepts { title?: string, description?: string }
}

updateTodo(1, { description: "Clean kitchen" }); // Perfectly valid!

2. Omit<T, Keys>

Strategically constructs a brand new Type natively by picking an old interface and banning specific keys cleanly.

interface UserProfile {
    id: string;
    username: string;
    passwordHash: string;
}

// We ban passwordHash securely from the frontend return object natively!
type SafeFrontendUser = Omit<UserProfile, "passwordHash">;

const publicUser: SafeFrontendUser = {
    id: "1",
    username: "Alice"
};

3. Pick<T, Keys>

The exact opposite inverse logic of Omit. It constructs a new Type natively strictly grabbing ONLY the explicitly allowed keys requested natively.

type UsernameOnly = Pick<UserProfile, "username">;

4. Record<Keys, Type>

Builds a mapping dictionary dynamically bridging a strict key classification natively against a strict value classification natively.

// Dictionary mapping a String Key against a Number Value mapped natively
const scoreBoard: Record<string, number> = {
    "Alice": 50,
    "Bob": 100
};