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unzip.ts
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unzip.ts
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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.
/**
* Builds two separate arrays from the given array of 2-tuples, with the first returned array holding all first
* tuple elements and the second one holding all the second elements
*
* Example:
*
* ```ts
* import { unzip } from "https://deno.land/std@$STD_VERSION/collections/mod.ts";
* import { assertEquals } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts";
*
* const parents = [
* [ 'Maria', 'Jeff' ],
* [ 'Anna', 'Kim' ],
* [ 'John', 'Leroy' ],
* ] as [string, string][];
*
* const [ moms, dads ] = unzip(parents);
*
* assertEquals(moms, [ 'Maria', 'Anna', 'John' ]);
* assertEquals(dads, [ 'Jeff', 'Kim', 'Leroy' ]);
* ```
*/
export function unzip<T, U>(pairs: readonly [T, U][]): [T[], U[]] {
const { length } = pairs;
const ret: [T[], U[]] = [
Array.from({ length }),
Array.from({ length }),
];
pairs.forEach(([first, second], index) => {
ret[0][index] = first;
ret[1][index] = second;
});
return ret;
}