Functions

ThisParameterType

Extracts the explicit `this` parameter from a function type.

What it is

A conditional extractor for TypeScript’s special fake first parameter. An explicit `this` annotation participates in type checking but is erased from JavaScript and is not part of `Parameters<T>`, so it needs its own utility when a wrapper or binder wants to recover it.

Examples

```
ThisParameterType<typeof toHex>
```
→Number

ThisParameterType<(this: { id: string }) => void>["id"]

→string

```
ThisParameterType<(value: number) => void>
```
→unknown
No explicit `this` parameter means `unknown`, not the global object or the containing class.

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

What it does not do

It does not return the first ordinary parameter. `this` has dedicated syntax and never appears in the emitted argument list.
It cannot discover a run-time receiver when the function type has no explicit annotation; the safe answer in that case is `unknown`.

Takeaway

An explicit `this` parameter is type-only and separate from ordinary parameters; `ThisParameterType` is the extractor made for that separate slot.