What are Mapped Types and how can you use them to transform an object?

Mapped types allow you to create new types based on the properties of an existing type by iterating over keys.

Mapped types use the keyof operator to iterate through keys of an existing type and apply a transformation. This is essential for creating variations of a type without duplicating code. You can add or remove modifiers like readonly or ? using the + or - prefix. Since TypeScript 4.1, you can also use 'Key Remapping' with the as clause to change the property names themselves during the mapping process.