TypeScript's keyof and Mapped Types

# TypeScript's keyof and Mapped Types

2025-07-14

The keyof operator and mapped types in TypeScript allow for advanced type manipulation. Here’s an example:

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

type UserKeys = keyof User; // 'id' | 'name' | 'email'

type ReadonlyUser = {
    [K in keyof User]: Readonly<User[K]>;
};

const user: ReadonlyUser = {
    id: 1,
    name: "John",
    email: "john@example.com"
};

// user.id = 2; // Error: Cannot assign to 'id' because it is a read-only property.

These features make TypeScript a powerful tool for creating robust and type-safe applications.

echo "Using keyof and mapped types in TypeScript"

# TypeScript's keyof and Mapped Types

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