40 lines
1.5 KiB
JavaScript
40 lines
1.5 KiB
JavaScript
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//#region src/map/keyBy.ts
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/**
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* Maps each entry of a Map based on a provided key-generating function.
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*
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* This function takes a Map and a function that generates a key from each value-key pair.
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* It returns a new Map where the keys are generated by the key function and the values are
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* the corresponding values from the original map. If multiple entries produce the same key,
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* the last value encountered will be used.
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*
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* @template K - The type of keys in the original Map.
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* @template V - The type of values in the original Map.
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* @template K2 - The type of keys to produce in the returned Map.
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* @param {Map<K, V>} map - The map of entries to be mapped.
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* @param {(value: V, key: K, object: Map<K, V>) => K2} getKeyFromEntry - A function that generates a key from a value-key pair.
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* @returns {Map<K2, V>} A Map where the generated keys are mapped to each entry's value.
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*
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* @example
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* const map = new Map([
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* ['x', { type: 'fruit', name: 'apple' }],
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* ['y', { type: 'fruit', name: 'banana' }],
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* ['z', { type: 'vegetable', name: 'carrot' }]
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* ]);
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* const result = keyBy(map, item => item.type);
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* // result will be:
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* // Map(2) {
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* // 'fruit' => { type: 'fruit', name: 'banana' },
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* // 'vegetable' => { type: 'vegetable', name: 'carrot' }
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* // }
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*/
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function keyBy(map, getKeyFromEntry) {
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const result = /* @__PURE__ */ new Map();
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for (const [key, value] of map) {
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const newKey = getKeyFromEntry(value, key, map);
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result.set(newKey, value);
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}
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return result;
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}
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//#endregion
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export { keyBy };
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