[Home](./index.md) > [rc-js-util](./rc-js-util.md) > [mapInitializeGet](./rc-js-util.mapinitializeget_1.md) ## mapInitializeGet() function Gets the value from a `Map` for a given key, where the value is `undefined` or hasn't been set, the callback's return will be inserted into the `Map` and returned. **Signature:** ```typescript export declare function mapInitializeGet(map: WeakMap, key: TKey, getValue: (key: TKey) => TValue): TMapValue; ``` ## Parameters

Parameter	Type	Description
map	WeakMap<TMapKey, TMapValue>	The `Map` to search and modify.
key	TKey	The key to search for / set in `map`.
getValue	(key: TKey) => TValue	The function to call if a value is not found.

**Returns:** TMapValue The value in `map`, otherwise the result of the `getValue`. ## Remarks See [mapInitializeGet()](./rc-js-util.mapinitializeget.md).