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// Copyright 2018-2026 the Deno authors. MIT license.
// This module is browser compatible.
/**
* Returns the first element that is the smallest 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 minimum element in.
* @param selector The function to get the value to compare from each element.
* The function receives the element and its index.
*
* @returns The first element that is the smallest value of the given function
* or undefined if there are no elements.
*
* @example Basic usage
* ```ts
* import { minBy } from "@std/collections/min-by";
* import { assertEquals } from "@std/assert";
*
* const people = [
* { name: "Anna", age: 34 },
* { name: "Kim", age: 42 },
* { name: "John", age: 23 },
* ];
*
* const personWithMinAge = minBy(people, (i) => i.age);
*
* assertEquals(personWithMinAge, { name: "John", age: 23 });
* ```
*
* @example Using the index parameter
* ```ts
* import { minBy } from "@std/collections/min-by";
* import { assertEquals } from "@std/assert";
*
* const array = [4, 3, 2, 1];
* const result = minBy(array, (_, index) => index);
*
* assertEquals(result, 4);
* ```
*/
export function minBy<T>(
array: Iterable<T>,
selector: (el: T, index: number) => number,
): T | undefined;
/**
* Returns the first element that is the smallest 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 minimum element in.
* @param selector The function to get the value to compare from each element.
* The function receives the element and its index.
*
* @returns The first element that is the smallest value of the given function
* or undefined if there are no elements.
*
* @example Basic usage
* ```ts
* import { minBy } from "@std/collections/min-by";
* import { assertEquals } from "@std/assert";
*
* const people = [
* { name: "Anna" },
* { name: "Kim" },
* { name: "John" },
* ];
*
* const personWithMinName = minBy(people, (person) => person.name);
*
* assertEquals(personWithMinName, { name: "Anna" });
* ```
*/
export function minBy<T>(
array: Iterable<T>,
selector: (el: T, index: number) => string,
): T | undefined;
/**
* Returns the first element that is the smallest 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 minimum element in.
* @param selector The function to get the value to compare from each element.
* The function receives the element and its index.
*
* @returns The first element that is the smallest value of the given function
* or undefined if there are no elements.
*
* @example Basic usage
* ```ts
* import { minBy } from "@std/collections/min-by";
* import { assertEquals } from "@std/assert";
*
* const people = [
* { name: "Anna", age: 34n },
* { name: "Kim", age: 42n },
* { name: "John", age: 23n },
* ];
*
* const personWithMinAge = minBy(people, (i) => i.age);
*
* assertEquals(personWithMinAge, { name: "John", age: 23n });
* ```
*/
export function minBy<T>(
array: Iterable<T>,
selector: (el: T, index: number) => bigint,
): T | undefined;
/**
* Returns the first element that is the smallest 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 minimum element in.
* @param selector The function to get the value to compare from each element.
* The function receives the element and its index.
*
* @returns The first element that is the smallest value of the given function
* or undefined if there are no elements.
*
* @example Basic usage
* ```ts
* import { minBy } from "@std/collections/min-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("2019-01-01") },
* ];
*
* const personWithMinStartedAt = minBy(people, (person) => person.startedAt);
* ```
*/
export function minBy<T>(
array: Iterable<T>,
selector: (el: T, index: number) => Date,
): T | undefined;
export function minBy<T>(
array: Iterable<T>,
selector:
| ((el: T, index: number) => number)
| ((el: T, index: number) => string)
| ((el: T, index: number) => bigint)
| ((el: T, index: number) => Date),
): T | undefined {
if (Array.isArray(array)) {
const length = array.length;
if (length === 0) return undefined;
let min: T = array[0]!;
let minValue = selector(min, 0);
for (let i = 1; i < length; i++) {
const current = array[i]!;
const currentValue = selector(current, i);
if (currentValue < minValue) {
min = current;
minValue = currentValue;
}
}
return min;
}
let index = 0;
const iter = array[Symbol.iterator]();
const first = iter.next();
if (first.done) return undefined;
let min: T = first.value;
let minValue = selector(min, index++);
let next = iter.next();
while (!next.done) {
const currentValue = selector(next.value, index++);
if (currentValue < minValue) {
min = next.value;
minValue = currentValue;
}
next = iter.next();
}
return min;
}
|