41 lines
1.2 KiB
JavaScript
41 lines
1.2 KiB
JavaScript
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//#region src/array/uniqBy.ts
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/**
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* Returns a new array containing only the unique elements from the original array,
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* based on the values returned by the mapper function.
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*
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* When duplicates are found, the first occurrence is kept and the rest are discarded.
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*
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* @template T - The type of elements in the array.
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* @template U - The type of mapped elements.
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* @param {T[]} arr - The array to process.
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* @param {(item: T) => U} mapper - The function used to convert the array elements.
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* @returns {T[]} A new array containing only the unique elements from the original array, based on the values returned by the mapper function.
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*
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* @example
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* ```ts
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* uniqBy([1.2, 1.5, 2.1, 3.2, 5.7, 5.3, 7.19], Math.floor);
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* // [1.2, 2.1, 3.2, 5.7, 7.19]
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* ```
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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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* uniqBy(array, item => item.category).length
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* // 2
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* ```
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*/
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function uniqBy(arr, mapper) {
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const map = /* @__PURE__ */ new Map();
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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 = mapper(item, i, arr);
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if (!map.has(key)) map.set(key, item);
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}
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return Array.from(map.values());
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}
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//#endregion
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exports.uniqBy = uniqBy;
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