38 lines
1.2 KiB
JavaScript
38 lines
1.2 KiB
JavaScript
import { uniqBy as uniqBy$1 } from "../../array/uniqBy.mjs";
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import { combineEagerAndLazyFunctions } from "../_internal/lazy.mjs";
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//#region src/fp/array/uniqBy.ts
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/**
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* Creates a function that removes duplicate values by mapped identity.
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*
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* The first value for each mapped key is preserved. The returned function is
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* lazy-capable inside {@link pipe}.
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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 comparison keys returned by the mapper.
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* @param mapper - Called with each value and index to produce a comparison key.
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* @returns A function that maps the piped array to unique values.
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*
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* @example
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* import { pipe, uniqBy } from 'es-toolkit/fp';
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*
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* pipe([{ id: 1 }, { id: 1 }, { id: 2 }], uniqBy(item => item.id));
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* // => [{ id: 1 }, { id: 2 }]
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*/
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function uniqBy(mapper) {
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function uniqByEager(array) {
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return uniqBy$1(array, (item, index) => mapper(item, index));
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}
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const uniqByLazy = (emit) => {
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const seen = /* @__PURE__ */ new Set();
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let index = 0;
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return (value) => {
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const key = mapper(value, index++);
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if (seen.has(key)) return true;
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seen.add(key);
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return emit(value);
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};
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};
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return combineEagerAndLazyFunctions(uniqByEager, uniqByLazy);
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}
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//#endregion
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export { uniqBy };
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