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# Interface: UnderlyingSourceStartCallback<R\>

[internal](../modules/internal-8.md).UnderlyingSourceStartCallback

## Type parameters

| Name |
| :------ |
| `R` |

## Callable

### UnderlyingSourceStartCallback

▸ **UnderlyingSourceStartCallback**(`controller`): `any`

#### Parameters

| Name | Type |
| :------ | :------ |
| `controller` | [`ReadableStreamController`](../modules/internal-8.md#readablestreamcontroller)<`R`\> |

#### Returns

`any`

#### Defined in

packages/medusa-js/node_modules/@types/node/stream/web.d.ts:100