Object shapes

Required

Removes ? from every property, one level deep.

What it is

The mirror of Partial, written with -?. The minus sign is the whole mechanism: modifiers in a mapped type can be added with +? and removed with -?, and Required is the standard library using the second. It also strips undefined from the property type, which is a separate effect people rarely expect.

Examples

```
Required<{ a?: string; b?: number }>
```
→{ a: string; b: number; }
```
Required<{ a?: string | undefined }>
```
→{ a: string; }
undefined goes too — -? removes it from the type, not only the ? from the key.
```
Required<{ a: string }>
```
→{ a: string; }

Each resolved type above was printed by TypeScript 6.0.3, not written by hand.

What it does not do

It does not make a property non-null. Required<{ a?: string | null }> still has null in it — only undefined is removed.
It is not deep either. The symmetry with Partial holds all the way to the limitation.

Takeaway

-? does two things at once: it removes the optionality and it removes undefined. Most confusion about Required is the second one arriving unannounced.