std/collections/map_not_nullish.ts

50 lines
1.5 KiB
TypeScript

// Copyright 2018-2024 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.
/**
* Returns a new array, containing all elements in the given array transformed
* using the given transformer, except the ones that were transformed to `null`
* or `undefined`.
*
* @typeParam T The type of the elements in the input array.
* @typeParam O The type of the elements in the output array.
*
* @param array The array to map elements from.
* @param transformer The function to transform each element.
*
* @returns A new array with all elements transformed by the given transformer,
* except the ones that were transformed to `null` or `undefined`.
*
* @example Basic usage
* ```ts
* import { mapNotNullish } from "@std/collections/map-not-nullish";
* import { assertEquals } from "@std/assert";
*
* const people = [
* { middleName: null },
* { middleName: "William" },
* { middleName: undefined },
* { middleName: "Martha" },
* ];
* const foundMiddleNames = mapNotNullish(people, (people) => people.middleName);
*
* assertEquals(foundMiddleNames, ["William", "Martha"]);
* ```
*/
export function mapNotNullish<T, O>(
array: Iterable<T>,
transformer: (el: T) => O,
): NonNullable<O>[] {
const result: NonNullable<O>[] = [];
for (const element of array) {
const transformedElement = transformer(element);
if (transformedElement !== undefined && transformedElement !== null) {
result.push(transformedElement as NonNullable<O>);
}
}
return result;
}