---
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/ae2968c38cf655c5b1b41f4c21f75adc7476180c/src/features/deps.ts#L35)

## Parameters

### id

`string`

### importer

`string` | `undefined`

## Returns

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