Typescript Utility Readonly

Readonly

Constructs a type with all properties of Type set to readonly, meaning the properties of the constructed type cannot be reassigned.

 interface Todo { title: string; } const todo: Readonly<Todo> = { title: "Delete inactive users", }; todo.title = "Hello"; 

Assigning a title to Todo Interface would throw an error .

Released:2.1

Reference: Official typescript docs