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|
// Copyright 2018-2025 the Deno authors. MIT license.
// This module is browser compatible.
/**
* Returns the first element that is the largest value of the given function or
* undefined if there are no elements.
*
* @typeParam T The type of the elements in the array.
*
* @param array The array to find the maximum element in.
* @param selector The function to get the value to compare from each element.
*
* @returns The first element that is the largest value of the given function or
* undefined if there are no elements.
*
* @example Basic usage
* ```ts
* import { maxBy } from "@std/collections/max-by";
* import { assertEquals } from "@std/assert";
*
* const people = [
* { name: "Anna", age: 34 },
* { name: "Kim", age: 42 },
* { name: "John", age: 23 },
* ];
*
* const personWithMaxAge = maxBy(people, (person) => person.age);
*
* assertEquals(personWithMaxAge, { name: "Kim", age: 42 });
* ```
*/
export function maxBy<T>(
array: Iterable<T>,
selector: (el: T) => number,
): T | undefined;
/**
* Returns the first element that is the largest value of the given function or
* undefined if there are no elements.
*
* @typeParam T The type of the elements in the array.
*
* @param array The array to find the maximum element in.
* @param selector The function to get the value to compare from each element.
*
* @returns The first element that is the largest value of the given function or
* undefined if there are no elements.
*
* @example Basic usage
* ```ts
* import { maxBy } from "@std/collections/max-by";
* import { assertEquals } from "@std/assert";
*
* const people = [
* { name: "Anna" },
* { name: "Kim" },
* { name: "John" },
* ];
*
* const personWithMaxName = maxBy(people, (person) => person.name);
*
* assertEquals(personWithMaxName, { name: "Kim" });
* ```
*/
export function maxBy<T>(
array: Iterable<T>,
selector: (el: T) => string,
): T | undefined;
/**
* Returns the first element that is the largest value of the given function or
* undefined if there are no elements.
*
* @typeParam T The type of the elements in the array.
*
* @param array The array to find the maximum element in.
* @param selector The function to get the value to compare from each element.
*
* @returns The first element that is the largest value of the given function or
* undefined if there are no elements.
*
* @example Basic usage
* ```ts
* import { maxBy } from "@std/collections/max-by";
* import { assertEquals } from "@std/assert";
*
* const people = [
* { name: "Anna", age: 34n },
* { name: "Kim", age: 42n },
* { name: "John", age: 23n },
* ];
*
* const personWithMaxAge = maxBy(people, (person) => person.age);
*
* assertEquals(personWithMaxAge, { name: "Kim", age: 42n });
* ```
*/
export function maxBy<T>(
array: Iterable<T>,
selector: (el: T) => bigint,
): T | undefined;
/**
* Returns the first element that is the largest value of the given function or
* undefined if there are no elements.
*
* @typeParam T The type of the elements in the array.
*
* @param array The array to find the maximum element in.
* @param selector The function to get the value to compare from each element.
*
* @returns The first element that is the largest value of the given function or
* undefined if there are no elements.
*
* @example Basic usage
* ```ts
* import { maxBy } from "@std/collections/max-by";
* import { assertEquals } from "@std/assert";
*
* const people = [
* { name: "Anna", startedAt: new Date("2020-01-01") },
* { name: "Kim", startedAt: new Date("2021-03-01") },
* { name: "John", startedAt: new Date("2020-03-01") },
* ];
*
* const personWithLastStartedAt = maxBy(people, (person) => person.startedAt);
*
* assertEquals(personWithLastStartedAt, { name: "Kim", startedAt: new Date("2021-03-01") });
* ```
*/
export function maxBy<T>(
array: Iterable<T>,
selector: (el: T) => Date,
): T | undefined;
export function maxBy<T>(
array: Iterable<T>,
selector:
| ((el: T) => number)
| ((el: T) => string)
| ((el: T) => bigint)
| ((el: T) => Date),
): T | undefined {
let max: T | undefined;
let maxValue: ReturnType<typeof selector> | undefined;
for (const current of array) {
const currentValue = selector(current);
if (maxValue === undefined || currentValue > maxValue) {
max = current;
maxValue = currentValue;
}
}
return max;
}
|