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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 | 1x 4x 1x 4x 4x 4x | import { compute } from "./compute";
/**
* @mutation
*
* @remark
* only returns `undefined` if `mappingFunction` returns `undefined`
*
* @example
* Set a {@link Map} entry if the key is absent
* ```ts
* const map = new Map([[1, 2]]);
* merge(map)(1, 3, (old, value) => old + value);
* console.log(map); // Map([[1, 5]])
* ```
*
* @typeParam K - the {@link Map} key type
* @typeParam V - the {@link Map} value type
* @param map - the {@link Map} to set the entry
*/
export const merge =
<K, V>(map: Map<K, V>) =>
(
key: K,
value: V,
remappingFunction: (oldValue: V | undefined, value: V) => V | undefined
): V | undefined => {
return compute(map)(key, (key, oldValue) =>
map.has(key) ? remappingFunction(oldValue, value) : value
);
};
|