es-toolkit
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A state-of-the-art, high-performance JavaScript utility library with a small bundle size and strong type annotations.
39 lines (38 loc) • 1.34 kB
JavaScript
//#region src/set/keyBy.ts
/**
* Maps each element of a Set based on a provided key-generating function.
*
* This function takes a Set and a function that generates a key from each value.
* It returns a new Map where the keys are generated by the key function and the values are
* the corresponding values from the original set. If multiple elements produce the same key,
* the last value encountered will be used.
*
* @template T - The type of elements in the Set.
* @template K - The type of keys to produce in the returned Map.
* @param set - The set of elements to be mapped.
* @param getKeyFromValue - A function that generates a key from a value.
* @returns A Map where the generated keys are mapped to each element's value.
*
* @example
* const set = new Set([
* { type: 'fruit', name: 'apple' },
* { type: 'fruit', name: 'banana' },
* { type: 'vegetable', name: 'carrot' }
* ]);
* const result = keyBy(set, item => item.type);
* // result will be:
* // Map(2) {
* // 'fruit' => { type: 'fruit', name: 'banana' },
* // 'vegetable' => { type: 'vegetable', name: 'carrot' }
* // }
*/
function keyBy(set, getKeyFromValue) {
const result = /* @__PURE__ */ new Map();
for (const value of set) {
const newKey = getKeyFromValue(value, value, set);
result.set(newKey, value);
}
return result;
}
//#endregion
export { keyBy };