isPlainObject

Checks if a value is a plain object.

const result = isPlainObject(value);

Reference

isPlainObject(value)

Use isPlainObject when you want to check if a value is a plain object. A plain object is an object created with an object literal ({}) or the Object constructor. Class instances, arrays, or other special objects are not plain objects.

import { isPlainObject } from 'es-toolkit/predicate';

// Plain objects
console.log(isPlainObject({})); // true
console.log(isPlainObject({ name: 'John', age: 30 })); // true
console.log(isPlainObject(Object.create(null))); // true
console.log(isPlainObject(new Object())); // true

// Non-plain objects
console.log(isPlainObject([])); // false (array)
console.log(isPlainObject(new Date())); // false (Date object)
console.log(isPlainObject(new Set())); // false (Set object)
console.log(isPlainObject(new Map())); // false (Map object)
console.log(isPlainObject(null)); // false (null)
console.log(isPlainObject(42)); // false (number)
console.log(isPlainObject('hello')); // false (string)

// Class instances
class MyClass {}
console.log(isPlainObject(new MyClass())); // false

It's useful when serializing data or validating configuration objects.

function processConfig(config: unknown) {
  if (isPlainObject(config)) {
    // config is now narrowed to Record<PropertyKey, any>
    console.log('Valid configuration object');
    Object.keys(config).forEach(key => {
      console.log(`${key}: ${config[key]}`);
    });
  } else {
    throw new Error('Configuration must be a plain object');
  }
}

Parameters

• value (unknown): The value to check if it's a plain object.

Returns

(value is Record<PropertyKey, any>): Returns true if the value is a plain object, false otherwise.

Performance Comparison

	Bundle Size	Runtime Performance
es-toolkit	279 bytes (82.4% smaller)	1,505,684 times (1.70× faster)
es-toolkit/compat	435 bytes (72.5% smaller)	2,013,760 times (2.28× faster)
lodash-es	1,586 bytes	882,669 times