rc-js-util/docs/rc-js-util.mapaddtoset.md

A collection of TS and C++ utilities to help writing performant and correct applications, achieved through strict typing and (removable) invariant checking.

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## mapAddToSet() function

Used with maps that store sets. Where a set exists for a given key the value will be added to that set, otherwise a new set will be created containing the value.

**Signature:**

```typescript
export declare function mapAddToSet<TKey, TValue>(map: Map<TKey, Set<TValue>>, key: TKey, value: TValue): void;
```

## Parameters

<table><thead><tr><th>

Parameter


</th><th>

Type


</th><th>

Description


</th></tr></thead>
<tbody><tr><td>

map


</td><td>

Map&lt;TKey, Set&lt;TValue&gt;&gt;


</td><td>

The `Map` to check. May be modified.


</td></tr>
<tr><td>

key


</td><td>

TKey


</td><td>

The key to lookup in `map`<!-- -->.


</td></tr>
<tr><td>

value


</td><td>

TValue


</td><td>

The value to add.


</td></tr>
</tbody></table>
**Returns:**

void

## Remarks

See [mapAddToSet()](./rc-js-util.mapaddtoset.md)<!-- -->.