Dev Dastan: post #46 — TG.ME

TypeScript Tips and Tricks Series (Part 4)

Previous Parts: [part 1 | Part 2 | Part 3]

Mapped Types

Transform existing types by applying operations to each property. Useful for adding prefixes/suffixes to properties, creating key-value pairs from objects, etc.

interface User {
  name: string;
  age: number;
}

type ReadOnly<T> = { readonly [P in keyof T]: T[P] };

const readOnlyUser: ReadOnly<User> = {
  name: 'Kurt',
  age: 27
};

// readOnlyUser.name = 'Chester';
// Error: Cannot assign to 'name' because it is a read-only property

Use Case:
Useful for manipulate and transform data from the API or before passing data to another component, with different data types.

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