46 lines
1.6 KiB
JavaScript
46 lines
1.6 KiB
JavaScript
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//#region src/array/keyBy.ts
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/**
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* Maps each element of an array based on a provided key-generating function.
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*
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* This function takes an array and a function that generates a key from each element. It returns
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* an object where the keys are the generated keys and the values are the corresponding elements.
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* If there are multiple elements generating the same key, the last element among them is used
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* as the value.
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*
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* @template T - The type of elements in the array.
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* @template K - The type of keys.
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* @param {T[]} arr - The array of elements to be mapped.
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* @param {(item: T, index: number, array: readonly T[]) => K} getKeyFromItem - A function that generates a key from an element, its index, and the array.
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* @returns {Record<K, T>} An object where keys are mapped to each element of an array.
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*
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* @example
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* const array = [
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* { category: 'fruit', name: 'apple' },
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* { category: 'fruit', name: 'banana' },
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* { category: 'vegetable', name: 'carrot' }
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* ];
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* const result = keyBy(array, item => item.category);
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* // result will be:
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* // {
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* // fruit: { category: 'fruit', name: 'banana' },
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* // vegetable: { category: 'vegetable', name: 'carrot' }
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* // }
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*
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* @example
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* // Using index parameter
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* const items = ['a', 'b', 'c'];
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* const result = keyBy(items, (item, index) => index);
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* // result will be: { 0: 'a', 1: 'b', 2: 'c' }
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*/
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function keyBy(arr, getKeyFromItem) {
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const result = {};
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for (let i = 0; i < arr.length; i++) {
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const item = arr[i];
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const key = getKeyFromItem(item, i, arr);
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result[key] = item;
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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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