keysIn (Lodash compatibility)

::: warning 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.

typescript

const allKeys = keysIn(object);

Usage

`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.

typescript

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.

typescript

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.

typescript

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.

typescript

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.