What do -readonly and -? do in a mapped type? type Mutable = { -readonly [K in keyof T]-?: T[K] };

Remove the readonly and ? modifiers from all properties

Add the readonly and ? modifiers to all properties

Delete the properties marked readonly from the type

TypeScript · Middle · Question 27 of 75

What do `-readonly` and `-?` do in a mapped type?

type Mutable<T> = { -readonly [K in keyof T]-?: T[K] };

✓Correct answer: Remove the readonly and ? modifiers from all properties
2Add the readonly and ? modifiers to all properties
3Delete the properties marked readonly from the type

Explanation

The - prefix removes a modifier, + (the default) adds it. That's how Required<T> is implemented (-?). There's no built-in Mutable, but it's often written following this pattern.

What do `-readonly` and `-?` do in a mapped type?

Explanation

Further reading

Problem with a question

Test yourself