---
url: /reference/api/TypeAlias.NoExternalFn.md
---
# Type Alias: NoExternalFn

```ts
type NoExternalFn = (id, importer) => boolean | null | undefined | void
```

Defined in: [src/features/deps.ts:35](https://github.com/rolldown/tsdown/blob/304e4cc26790ca450f4dde821833a3b501481439/src/features/deps.ts#L35)

## Parameters

### id

`string`

### importer

`string` | `undefined`

## Returns

`boolean` | `null` | `undefined` | `void`