Module

std/collections/distinct_by.ts

Deno standard library
Go to Latest
File
// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.// This module is browser compatible.
/** * Returns all elements in the given array that produce a distinct value using the given selector, preserving order by first occurrence * * Example: * * ```ts * import { distinctBy } from "https://deno.land/std@$STD_VERSION/collections/mod.ts"; * import { assertEquals } from "https://deno.land/std@$STD_VERSION/testing/asserts.ts"; * * const names = [ 'Anna', 'Kim', 'Arnold', 'Kate' ] * const exampleNamesByFirstLetter = distinctBy(names, it => it.charAt(0)) * * assertEquals(exampleNamesByFirstLetter, [ 'Anna', 'Kim' ]) * ``` */export function distinctBy<T, D>( array: readonly T[], selector: (el: T) => D,): T[] { const selectedValues = new Set<D>(); const ret: T[] = [];
for (const element of array) { const currentSelectedValue = selector(element);
if (!selectedValues.has(currentSelectedValue)) { selectedValues.add(currentSelectedValue); ret.push(element); } }
return ret;}