Array.prototype.findLastIndex()

findLastIndex(callbackFn, thisArg)

Returns: number · Added in vES2023 · Updated March 13, 2026 · Array Methods

array find search es2023

findLastIndex() returns the index of the last element in an array that satisfies a testing function, or -1 if no element matches. It iterates from the end of the array toward the beginning.

Syntax

findLastIndex(callbackFn)
findLastIndex(callbackFn, thisArg)

Parameters

Parameter	Type	Default	Description
`callbackFn`	`function`	—	A function to execute for each element. Return `true` to signal a match.
`thisArg`	`any`	`undefined`	Optional. Value to use as `this` when executing `callbackFn`.

callbackFn Parameters

Parameter	Type	Description
`element`	`any`	The current element being processed.
`index`	`number`	The index of the current element.
`array`	`array`	The array that `findLastIndex` was called on.

Examples

Basic usage

const nums = [5, 12, 8, 130, 44];

const lastEvenIndex = nums.findLastIndex(n => n % 2 === 0);
console.log(lastEvenIndex);
// 4

Finding the index of the last matching object

const users = [
  { id: 1, name: "Alice", active: true },
  { id: 2, name: "Bob", active: false },
  { id: 3, name: "Charlie", active: true },
  { id: 4, name: "Diana", active: true }
];

const lastActiveIndex = users.findLastIndex(u => u.active);
console.log(lastActiveIndex);
// 3

When no match is found

const nums = [1, 3, 5, 7];

const index = nums.findLastIndex(n => n > 10);
console.log(index);
// -1

Common Patterns

Removing the last matching item

Combine findLastIndex with splice to remove the last matching element:

const items = ["a", "b", "c", "b", "d"];
const idx = items.findLastIndex(x => x === "b");

const removed = items.splice(idx, 1);
console.log(removed);
// ["b"]
console.log(items);
// ["a", "c", "b", "d"]