```typescript
import { types } from "node:node__util.d.ts";
```
isWeakSet(object: unknown): object is WeakSet<object>
Returns `true` if the value is a built-in [`WeakSet`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WeakSet) instance.
```js
util.types.isWeakSet(new WeakSet()); // Returns true
```