findKey (Lodash compatibility)

::: warning Use es-toolkit's findKey

This findKey function operates in a complex manner due to various condition type handling and compatibility logic.

Instead, use the faster and more modern findKey from es-toolkit.

:::

Finds the key of the first element that matches the predicate.

const key = findKey(obj, predicate);

Usage

findKey(obj, predicate)

Use findKey to find the key of the first element in an object that matches the predicate. You can use various types of predicates such as functions, objects, arrays, and strings.

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

// Find key with a function predicate
const users = {
  alice: { age: 25, active: true },
  bob: { age: 30, active: false },
  charlie: { age: 35, active: true },
};

findKey(users, user => user.age > 30);
// Returns: 'charlie'

// Find key with an object predicate
findKey(users, { active: false });
// Returns: 'bob'

// Find key with a property path
findKey(users, 'active');
// Returns: 'alice'

If no element matches the predicate, it returns undefined.

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

findKey({ a: 1, b: 2 }, value => value > 5);
// Returns: undefined

Parameters

• obj (T | null | undefined): The object to search.
• predicate (ObjectIteratee<T>, optional): The predicate to apply to each element. Can be a function, object, array, or string.

Returns

(string | undefined): Returns the key of the first element that matches the predicate. Returns undefined if no match is found.