findLastKey

INFO

This function is only available in es-toolkit/compat for compatibility reasons. It either has alternative native JavaScript APIs or isn't fully optimized yet.

When imported from es-toolkit/compat, it behaves exactly like lodash and provides the same functionalities, as detailed here.

Returns the key of the last element that satisfies the provided predicate.

Unlike findKey which searches from the beginning, findLastKey searches from the end of the object.

Signature

function findLastKey<T>(
  obj: T | null | undefined,
  conditionToFind: (value: T[keyof T], key: string, obj: T) => unknown
): string | undefined;

function findLastKey<T>(obj: T | null | undefined, objectToFind: Partial<T[keyof T]>): string | undefined;

function findLastKey<T>(obj: T | null | undefined, propertyToFind: [PropertyKey, any]): string | undefined;

function findLastKey<T>(obj: T | null | undefined, propertyToFind: PropertyKey): string | undefined;

function findLastKey<T>(
  obj: T | null | undefined,
  predicate?:
    | ((value: T[keyof T], key: string, obj: T) => unknown)
    | PropertyKey
    | [PropertyKey, any]
    | Partial<T[keyof T]>
): string | undefined;

Parameters

• obj (T | null | undefined): The object to inspect.
• predicate: The function invoked per iteration. Can be one of:
  • (value, key, obj) => unknown - The function executed for each element.
  • Partial<T[keyof T]> - Matches elements that have matching properties.
  • [PropertyKey, any] - Matches elements with the specified property and value.
  • PropertyKey - Matches elements with truthy values for the specified property.

Returns

(string | undefined): Returns the key of the matched element, else undefined.

Examples

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

const users = {
  barney: { age: 36, active: true },
  fred: { age: 40, active: false },
  pebbles: { age: 1, active: true },
};

// Using a function predicate
findLastKey(users, o => o.age < 40);
// => 'pebbles'

// Using a partial object
findLastKey(users, { active: true });
// => 'pebbles'

// Using a property-value pair
findLastKey(users, ['active', false]);
// => 'fred'

// Using a property name (truthy)
findLastKey(users, 'active');
// => 'pebbles'