// Copyright 2018-2026 the Deno authors. MIT license.
// This module is browser compatible.
/**
* Applies the given selector to all elements of the provided collection and
* returns the max value of all elements. If an empty array is provided the
* function will return undefined.
*
* @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 largest value of the given function or undefined if there are no
* elements.
*
* @example Basic usage
* ```ts
* import { maxOf } from "@std/collections/max-of";
* import { assertEquals } from "@std/assert";
*
* const inventory = [
* { name: "mustard", count: 2 },
* { name: "soy", count: 4 },
* { name: "tomato", count: 32 },
* ];
*
* const maxCount = maxOf(inventory, (item) => item.count);
*
* assertEquals(maxCount, 32);
* ```
*/
export function maxOf<T>(
array: Iterable<T>,
selector: (el: T) => number,
): number | undefined;
/**
* Applies the given selector to all elements of the provided collection and
* returns the max value of all elements. If an empty array is provided the
* function will return undefined.
*
* @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 { maxOf } from "@std/collections/max-of";
* import { assertEquals } from "@std/assert";
*
* const inventory = [
* { name: "mustard", count: 2n },
* { name: "soy", count: 4n },
* { name: "tomato", count: 32n },
* ];
*
* const maxCount = maxOf(inventory, (i) => i.count);
*
* assertEquals(maxCount, 32n);
* ```
*/
export function maxOf<T>(
array: Iterable<T>,
selector: (el: T) => bigint,
): bigint | undefined;
export function maxOf<T, S extends ((el: T) => number) | ((el: T) => bigint)>(
array: Iterable<T>,
selector: S,
): ReturnType<S> | undefined {
if (Array.isArray(array)) {
const length = array.length;
if (length === 0) return undefined;
let max = selector(array[0]!) as ReturnType<S>;
if (Number.isNaN(max)) return max;
for (let i = 1; i < length; i++) {
const currentValue = selector(array[i]!) as ReturnType<S>;
if (currentValue > max) {
max = currentValue;
} else if (Number.isNaN(currentValue)) {
return currentValue;
}
}
return max;
}
const iter = array[Symbol.iterator]();
const first = iter.next();
if (first.done) return undefined;
let max = selector(first.value) as ReturnType<S>;
if (Number.isNaN(max)) return max;
let next = iter.next();
while (!next.done) {
const currentValue = selector(next.value) as ReturnType<S>;
if (currentValue > max) {
max = currentValue;
} else if (Number.isNaN(currentValue)) {
return currentValue;
}
next = iter.next();
}
return max;
}
|