28 lines
No EOL
1.2 KiB
TypeScript
28 lines
No EOL
1.2 KiB
TypeScript
//#region src/fp/array/flatMap.d.ts
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/**
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* Creates a function that maps every element to an array with `callback` and
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* concatenates the results, equivalent to `Array.prototype.flatMap`. Use it
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* with {@link pipe}.
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*
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* The returned function is **lazy-capable**: inside a {@link pipe} it is fused
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* with adjacent lazy functions and runs element-by-element, so a trailing
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* `take` can terminate the walk early without expanding the rest of the input.
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*
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* @template T - The type of elements in the input array.
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* @template U - The type of elements in the output array.
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* @param callback - Called with `(value, index)` for each element; returns an
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* array whose elements are flattened into the output.
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* @returns A function that maps a `readonly T[]` to a new `U[]`.
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*
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* @example
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* import { pipe, flatMap } from 'es-toolkit/fp';
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*
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* pipe([1, 2, 3], flatMap(x => [x, x * 10])); // => [1, 10, 2, 20, 3, 30]
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*
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* @example
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* // Returning an empty array drops the element.
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* pipe([1, 2, 3, 4], flatMap(x => (x % 2 === 0 ? [x] : []))); // => [2, 4]
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*/
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declare function flatMap<T, U>(callback: (value: T, index: number) => U[]): (array: readonly T[]) => U[];
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//#endregion
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export { flatMap }; |