rc-js-util/docs/rc-js-util.mapfirstkey.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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## mapFirstKey() function

Gets the first inserted key in a `Map`<!-- -->.

**Signature:**

```typescript
export declare function mapFirstKey<K, V>(map: Map<K, V>): K | undefined;
```

## Parameters

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

Parameter


</th><th>

Type


</th><th>

Description


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

map


</td><td>

Map&lt;K, V&gt;


</td><td>


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

K \| undefined

The first key in `map`<!-- -->, otherwise `undefined` where size 0.

## Remarks

See [mapFirstKey()](./rc-js-util.mapfirstkey.md)<!-- -->.