Mapped Type Modifiers

Mapped Type Modifiers in TypeScript enable the transformation of properties within an existing type:

• readonly or +readonly: This renders a property in the mapped type as read-only.
• -readonly: This allows a property in the mapped type to be mutable.
• ?: This designates a property in the mapped type as optional.

Examples:

type ReadOnly<T> = { readonly [P in keyof T]: T[P] }; // All properties marked as read-only

type Mutable<T> = { -readonly [P in keyof T]: T[P] }; // All properties marked as mutable

type MyPartial<T> = { [P in keyof T]?: T[P] }; // All properties marked as optional