Object shapes

Pick

Keeps only the named keys, and checks that they exist.

What it is

A mapped type over K rather than over keyof T, which is why the result is a plain object rather than a copy of the original. The constraint K extends keyof T is doing real work: pick a key that is not there and the error arrives at the type, not later at a property access.

Examples

```
Pick<{ a: string; b: number }, 'a'>
```
→{ a: string; }

Pick<{ a: string; b: number; c: boolean }, 'a' | 'c'>

→{ a: string; c: boolean; }

```
Pick<{ readonly a: string }, 'a'>
```
→{ readonly a: string; }
readonly is carried across, because Pick maps over a key set derived from T.

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

What it does not do

It does not accept keys that are missing. That is a feature, and it is the difference between Pick and Omit — the latter accepts anything.
It does not distribute over a union in T. Pick<A | B, K> picks from the union as one thing rather than from each member.

Takeaway

When you want a subset and you want to be told about typos, Pick is the one with the guard rail.