39 lines
1.4 KiB
JavaScript
39 lines
1.4 KiB
JavaScript
const require_take = require("../../array/take.js");
|
|
const require_lazy = require("../_internal/lazy.js");
|
|
//#region src/fp/array/take.ts
|
|
/**
|
|
* Creates a function that returns the first `count` elements of an array. If
|
|
* `count` is greater than the array length, the whole array is returned. Use it
|
|
* with {@link pipe}.
|
|
*
|
|
* The returned function is **lazy-capable** for a non-negative integer `count`:
|
|
* inside a {@link pipe} it stops the walk as soon as `count` elements have been
|
|
* collected, so preceding lazy functions never process the rest of the input.
|
|
*
|
|
* @template T - The type of elements in the array.
|
|
* @param count - The number of elements to take from the front of the array.
|
|
* @returns A function that maps a `readonly T[]` to a new `T[]`.
|
|
*
|
|
* @example
|
|
* import { pipe, take } from 'es-toolkit/fp';
|
|
*
|
|
* pipe([1, 2, 3, 4, 5], take(3)); // => [1, 2, 3]
|
|
*
|
|
* @example
|
|
* // Early termination: `map` only runs three times.
|
|
* pipe([1, 2, 3, 4, 5], map(expensive), take(3));
|
|
*/
|
|
function take(count) {
|
|
function takeEager(array) {
|
|
return require_take.take(array, count);
|
|
}
|
|
if (!Number.isInteger(count) || count < 0) return takeEager;
|
|
const takeLazy = require_lazy.createLazyFunction((value, index, emit) => {
|
|
if (index >= count) return false;
|
|
emit(value);
|
|
return index < count - 1;
|
|
});
|
|
return require_lazy.combineEagerAndLazyFunctions(takeEager, takeLazy, { shortCircuit: true });
|
|
}
|
|
//#endregion
|
|
exports.take = take;
|