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partition.ts
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partition.ts
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// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
// This module is browser compatible.
/**
* Returns a tuple of two arrays with the first one containing all elements in the given array that match the given predicate
* and the second one containing all that do not
*
* Example:
*
* ```ts
* import { partition } from "https://deno.land/std@$STD_VERSION/collections/mod.ts";
* import { assertEquals } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts";
*
* const numbers = [ 5, 6, 7, 8, 9 ]
* const [ even, odd ] = partition(numbers, it => it % 2 == 0)
*
* assertEquals(even, [ 6, 8 ])
* assertEquals(odd, [ 5, 7, 9 ])
* ```
*/
export function partition<T>(
array: readonly T[],
predicate: (el: T) => boolean,
): [T[], T[]] {
const matches: Array<T> = [];
const rest: Array<T> = [];
for (const element of array) {
if (predicate(element)) {
matches.push(element);
} else {
rest.push(element);
}
}
return [matches, rest];
}