# Find the index of the last matching item of an array

Scan from the end and return the first index whose item matches.

Canonical: https://1loc.dev/array/find-the-index-of-the-last-matching-item-of-an-array/
Version: 1.0.0
Runtime: JavaScript · Node.js 22 / modern browsers
Verification: Usage lines executed in Node.js 22 and headless Chromium; no external services
Updated: 2026-10-28

## Implementation

```javascript
function lastIndex(values, predicate) { return values.findLastIndex(predicate); }
```

## Usage

```javascript
lastIndex([1, 3, 5, 7, 9, 2, 4, 6, 8], n => n % 2 === 1); // → 4
lastIndex([1, 3, 5, 7, 9, 8, 6, 4, 2], n => n > 6); // → 5
lastIndex([], () => true); // → -1
```

Lines marked → were executed in Node.js 22 and in headless Chromium, and each result was compared with the value shown. Lines marked e.g. are illustrative.

## Limits

- Array.prototype.findLastIndex is ES2023: Node.js 18+ and current browsers. The original reduced the whole array; findLastIndex stops at the first match from the end.

The function does not validate its arguments. Add checks where it receives untrusted input.

## Source and license

Original: https://github.com/phuocng/1loc/blob/14b481cf60dff1620ab1bb99a43b1f68068cdd9b/contents/find-the-index-of-the-last-matching-item-of-an-array.mdx
Author: Nguyen Huu Phuoc and original contributors
Contributors: See original repository history
Source commit: 14b481cf60dff1620ab1bb99a43b1f68068cdd9b
Copyright (c) 2020 phuoc-ng
License: MIT — https://1loc.dev/licenses/
Maintainer: Oveyon
Modifications: Uses Array.prototype.findLastIndex (ES2023). Documented as a reference with executed usage lines. Original MDX retained as inert source evidence.