# RefHashMap.has

Check if a key exists in the RefHashMap.

## Signatures

```ts
export declare const has: {
    <K>(key: K): <V, E, R>(ref: RefHashMap<K, V, E, R>) => RefSubject.Computed<boolean, E, R>;
    <K, V, E, R>(ref: RefHashMap<K, V, E, R>, key: K): RefSubject.Computed<boolean, E, R>;
};
```

## Why

Makes has a live projection of the hash map; consumers can sample it now or observe it without
copying the source state.

## Ownership and lifetime

The has view retains no independent state. An Effect read samples the source once; Fx
observation follows later pushes and its observing Scope owns subscription cleanup.