lastIndexOf (Lodash compatibility)

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);

Reference

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.