keysIn (Lodash compatibility)

Use for...in loop or Object.keys

This keysIn function operates slowly due to complex logic such as handling array-like objects and traversing the prototype chain.

Use the faster and more modern for...in loop or Object.keys() as needed instead.

Returns an array of all enumerable property names of an object, including inherited properties.

const allKeys = keysIn(object);

Reference

keysIn(object)

Use keysIn when you want to get all property names of an object including inherited properties. Unlike keys, it also returns properties from the prototype chain.

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

// Keys of a basic object
const object = { a: 1, b: 2 };
keysIn(object);
// => ['a', 'b']

// Indices of an array
const array = [1, 2, 3];
keysIn(array);
// => ['0', '1', '2']

// Indices of a string
keysIn('hello');
// => ['0', '1', '2', '3', '4']

It also includes inherited properties.

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

function Foo() {
  this.a = 1;
  this.b = 2;
}
Foo.prototype.c = 3;

keysIn(new Foo());
// => ['a', 'b', 'c'] (includes prototype property 'c')

// constructor is excluded
class MyClass {
  constructor() {
    this.prop = 1;
  }
  method() {}
}
MyClass.prototype.inherited = 2;

keysIn(new MyClass());
// => ['prop', 'method', 'inherited'] (constructor is excluded)

It specially handles array-like objects.

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

// TypedArray
const typedArray = new Uint8Array([1, 2, 3]);
keysIn(typedArray);
// => ['0', '1', '2'] (excludes buffer, byteLength, etc.)

// arguments object
function example() {
  return keysIn(arguments);
}
example('a', 'b', 'c');
// => ['0', '1', '2']

It safely handles null or undefined.

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

keysIn(null);
// => []

keysIn(undefined);
// => []

Parameters

• object (any): The object to get keys from.

Returns

(string[]): Returns an array of all enumerable property names (including both own and inherited properties) of the object.