[Home](./index.md) > [rc-js-util](./rc-js-util.md) > [mapFirstKey](./rc-js-util.mapfirstkey.md) ## mapFirstKey() function Gets the first inserted key in a `Map`. **Signature:** ```typescript export declare function mapFirstKey(map: Map): K | undefined; ``` ## Parameters

Parameter	Type	Description
map	Map<K, V>

**Returns:** K \| undefined The first key in `map`, otherwise `undefined` where size 0. ## Remarks See [mapFirstKey()](./rc-js-util.mapfirstkey.md).