Object.hasOwn()

Object.hasOwn(obj, prop)

Object.hasOwn() is a static method that returns true if the specified object has the indicated property as its own property. If the property is inherited or does not exist, it returns false.

Syntax

Object.hasOwn(obj, prop)

Parameters

Parameter	Type	Default	Description
obj	object	—	The object to check
prop	string | symbol	—	The property name or Symbol to check

Examples

Basic usage

const obj = { name: 'Alice', age: 30 };

console.log(Object.hasOwn(obj, 'name'));
// true

console.log(Object.hasOwn(obj, 'age'));
// true

console.log(Object.hasOwn(obj, 'gender'));
// false

Inherited properties return false

const parent = { a: 1 };
const child = Object.create(parent);
child.b = 2;

console.log(Object.hasOwn(child, 'a'));
// false — inherited from parent

console.log(Object.hasOwn(child, 'b'));
// true — own property

Checking Symbol properties

const sym = Symbol('id');
const obj = { [sym]: 123 };

console.log(Object.hasOwn(obj, sym));
// true

Common Patterns

Filtering own properties in loops

const parent = { inherited: 1 };
const child = Object.create(parent);
child.own = 2;
child.another = 3;

for (const key in child) {
  if (Object.hasOwn(child, key)) {
    console.log(key); // logs: 'own', 'another'
  }
}

Safe property checking before deletion

function safeDelete(obj, prop) {
  if (Object.hasOwn(obj, prop)) {
    delete obj[prop];
    return true;
  }
  return false;
}

Object.hasOwn() vs ObjecthasOwnProperty()

Object.hasOwn() is essentially a replacement for ObjecthasOwnProperty(). Key differences:

• Syntax: Object.hasOwn(obj, prop) vs obj.hasOwnProperty(prop)
• Null safety: Object.hasOwn() throws TypeError if obj is null/undefined (unlike hasOwnProperty which would silently fail)
• Modern: Object.hasOwn() is the recommended approach for new code

const obj = { a: 1 };

// Both work for normal objects
obj.hasOwnProperty('a');       // true
Object.hasOwn(obj, 'a');       // true

// But with null/undefined:
Object.hasOwn(null, 'a');     // TypeError
Object.hasOwn(undefined, 'a'); // TypeError

See Also

• object::keys — Get object keys
• object::entries — Get object entries