lastIndexOf (Lodash compatibility)

::: warning Use Array.lastIndexOf

This lastIndexOf function operates slowly due to handling null or undefined, searching for NaN values, etc.

Instead, use the faster and more modern Array.lastIndexOf.

:::

Finds the last index at which a given element appears in an array.

const index = lastIndexOf(array, searchElement, fromIndex);

Usage

lastIndexOf(array, searchElement, fromIndex)

Returns the last index at which a given element appears in an array. Similar to native Array.lastIndexOf but can also find NaN values.

import { lastIndexOf } from 'es-toolkit/compat';

// Basic usage
lastIndexOf([1, 2, 1, 2], 2);
// => 3

// Specifying a start index
lastIndexOf([1, 2, 1, 2], 2, 2);
// => 1

// Finding NaN values (native lastIndexOf cannot find NaN)
lastIndexOf([1, 2, NaN, 4, NaN], NaN);
// => 4

// Using negative index
lastIndexOf([1, 2, 3, 4], 3, -2);
// => 2

null or undefined are treated as empty arrays.

import { lastIndexOf } from 'es-toolkit/compat';

lastIndexOf(null, 1); // -1
lastIndexOf(undefined, 1); // -1

Parameters

• array (ArrayLike<T> | null | undefined): The array to search.
• searchElement (T): The element to find.
• fromIndex (true | number, optional): The index to start searching from. Passing true searches from the end of the array. Defaults to array.length - 1.

Returns

(number): Returns the index of the last matching element. Returns -1 if not found.