Object.hasOwn() Method – Check If an Object Owns a Property Directly

Whenever you use Object.hasOwn() on a JavaScript object, the method does the following:

• It checks if the object owns the specified property as its direct property—not as its inherited property.
• It returns true if the object has the specified property as its own property. Otherwise, it returns false.

Syntax of the Object.hasOwn() Method

Object.hasOwn() accepts two arguments. Here’s the syntax:

Object.hasOwn(obj, prop);

• The obj argument refers to the JavaScript object you want to test.
• The prop argument is the name of the property you wish to find in the specified object.

Examples of the Object.hasOwn() Method

Below are examples of the Object.hasOwn() method.

Check if profile has its own firstName property

const profile = {
  firstName: "Oluwatobi",
  lastName: "Sofela",
  companyName: "CodeSweetly",
  profession: "Developer",
};

Object.hasOwn(profile, "firstName");

// The invocation above will return: true

Try Editing It

The snippet above returned true because firstName is one of the profile object’s direct properties.

Check if profile has its own companyName property

const profile = {
  firstName: "Oluwatobi",
  lastName: "Sofela",
  companyName: "CodeSweetly",
  profession: "Developer",
};

Object.hasOwn(profile, "companyName");

// The invocation above will return: true

Try Editing It

The snippet above returned true because companyName is one of the profile object’s own properties.

Check if profile has its own website property

const profile = {
  firstName: "Oluwatobi",
  lastName: "Sofela",
  companyName: "CodeSweetly",
  profession: "Developer",
};

Object.hasOwn(profile, "website");

// The invocation above will return: false

Try Editing It

The snippet above returned false because website is not part of the profile object’s direct properties.

Check if profile has its own valueOf property

const profile = {
  firstName: "Oluwatobi",
  lastName: "Sofela",
  companyName: "CodeSweetly",
  profession: "Developer",
};

Object.hasOwn(profile, "valueOf");

// The invocation above will return: false

Try Editing It

The snippet above returned false because valueOf is not part of the profile object’s own properties—although it is one of its inherited properties.

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Object.hasOwn vs. Object.prototype.hasOwnProperty()

Developers prefer Object.hasOwn() to the Object.prototype.hasOwnProperty() method because hasOwn() accepts the objects you create using Object.create(null).

For instance, consider the following code:

const profile = Object.create(null);

profile.firstName = "Oluwatobi";

profile.hasOwnProperty("firstName");

// The invocation above will return:
// Uncaught TypeError: profile.hasOwnProperty is not a function

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JavaScript threw an error because the hasOwnProperty() method does not work with the objects you create using the Object.create(null) method. However, hasOwn() accepts such objects.

Here’s an example:

const profile = Object.create(null);

profile.firstName = "Oluwatobi";

Object.hasOwn(profile, "firstName");

// The invocation above will return: true

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Object.hasOwn vs. the in Keyword

The Object.hasOwn() method checks an object for its own (direct) properties only.

However, the in keyword allows you to check an object for its direct (own) and indirect (inherited) properties.

For instance, consider the following code:

const profile = {
  firstName: "Oluwatobi",
  lastName: "Sofela",
  companyName: "CodeSweetly",
  profession: "Developer",
};

Object.hasOwn(profile, "constructor");

// The invocation above will return: false

Try Editing It

The snippet above returned false because constructor is not part of the profile object’s direct properties.

Note that constructor is one of the profile object’s inherited properties, but hasOwn finds only direct properties. You can, however, use the in keyword to find inherited properties.

Here’s an example:

const profile = {
  firstName: "Oluwatobi",
  lastName: "Sofela",
  companyName: "CodeSweetly",
  profession: "Developer",
};

"constructor" in profile;

// The invocation above will return: true

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