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// Copyright 2018-2025 the Deno authors. MIT license.
// This module is browser compatible.
/** Order option for {@linkcode SortByOptions}. */
export type Order = "asc" | "desc";
/** Options for {@linkcode sortBy}. */
export type SortByOptions = {
/**
* The order to sort the elements in.
*
* @default {"asc"}
*/
order: Order;
};
/**
* Types that can be compared with other values of the same type
* using comparison operators.
*/
export type Comparable = number | string | bigint | Date;
/**
* Returns all elements in the given collection, sorted by their result using
* the given selector. The selector function is called only once for each
* element. Ascending or descending order can be specified through the `order`
* option. By default, the elements are sorted in ascending order.
*
* @experimental **UNSTABLE**: New API, yet to be vetted.
*
* @typeParam T The type of the iterator elements.
* @typeParam U The type of the selected values.
*
* @param iterator The iterator to sort.
* @param selector The selector function to get the value to sort by.
* @param options The options for sorting.
*
* @returns A new array containing all elements sorted by the selector.
*
* @example Usage with numbers
* ```ts
* import { sortBy } from "@std/collections/sort-by";
* import { assertEquals } from "@std/assert";
*
* const people = [
* { name: "Anna", age: 34 },
* { name: "Kim", age: 42 },
* { name: "John", age: 23 },
* ];
* const sortedByAge = sortBy(people, (person) => person.age);
*
* assertEquals(sortedByAge, [
* { name: "John", age: 23 },
* { name: "Anna", age: 34 },
* { name: "Kim", age: 42 },
* ]);
*
* const sortedByAgeDesc = sortBy(people, (person) => person.age, { order: "desc" });
*
* assertEquals(sortedByAgeDesc, [
* { name: "Kim", age: 42 },
* { name: "Anna", age: 34 },
* { name: "John", age: 23 },
* ]);
* ```
*
* @example Usage with strings
* ```ts
* import { sortBy } from "@std/collections/sort-by";
* import { assertEquals } from "@std/assert";
*
* const people = [
* { name: "Anna" },
* { name: "Kim" },
* { name: "John" },
* ];
* const sortedByName = sortBy(people, (it) => it.name);
*
* assertEquals(sortedByName, [
* { name: "Anna" },
* { name: "John" },
* { name: "Kim" },
* ]);
* ```
*
* @example Usage with bigints
* ```ts
* import { sortBy } from "@std/collections/sort-by";
* import { assertEquals } from "@std/assert";
*
* const people = [
* { name: "Anna", age: 34n },
* { name: "Kim", age: 42n },
* { name: "John", age: 23n },
* ];
*
* const sortedByAge = sortBy(people, (person) => person.age);
*
* assertEquals(sortedByAge, [
* { name: "John", age: 23n },
* { name: "Anna", age: 34n },
* { name: "Kim", age: 42n },
* ]);
* ```
*
* @example Usage with Date objects
* ```ts
* import { sortBy } from "@std/collections/sort-by";
* import { assertEquals } from "@std/assert";
*
* const people = [
* { name: "Anna", startedAt: new Date("2020-01-01") },
* { name: "Kim", startedAt: new Date("2020-03-01") },
* { name: "John", startedAt: new Date("2020-06-01") },
* ];
*
* const sortedByStartedAt = sortBy(people, (people) => people.startedAt);
*
* assertEquals(sortedByStartedAt, [
* { name: "Anna", startedAt: new Date("2020-01-01") },
* { name: "Kim", startedAt: new Date("2020-03-01") },
* { name: "John", startedAt: new Date("2020-06-01") },
* ]);
* ```
*/
export function sortBy<T, U extends Comparable>(
iterator: Iterable<T>,
selector: (el: T) => U,
options?: SortByOptions,
): T[] {
const array: { value: T; selected: U }[] = [];
for (const item of iterator) {
array.push({ value: item, selected: selector(item) });
}
array.sort((oa, ob) => {
const a = oa.selected;
const b = ob.selected;
const order = options?.order === "desc" ? -1 : 1;
if (Number.isNaN(a)) return order;
if (Number.isNaN(b)) return -order;
return order * (a > b ? 1 : a < b ? -1 : 0);
});
return array.map((item) => item.value);
}
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