What is the hasOwnProperty function in JavaScript?

The hasOwnProperty function in JavaScript is used to determine whether or not a particular property belongs to a predefined object.

Syntax

``` Object.hasOwnProperty(property) ```

Parameters

The ``hasOwnProperty`` takes in only one parameter:

• property - the name of the property to check. Can either be of type Symbol or String.

Return value

The ``hasOwnProperty`` function returns a boolean value. If the property belongs to the object being tested, ``true`` is returned. Otherwise, `false` is returned.

The function only returns true if the property being tested is a direct property instead of an inherited one.

An inherited property is one that exists in the object’s prototype chain. A direct property is the object’s own property and does not belong to its prototype chain.

The function returns true for undefined or null direct properties of the object as well.

Example

The program below demonstrates how to use the ``hasOwnProperty`` function. We declare an object named ``person``, which contains the first name, last name, and age of a person.

The hasOwnProperty function is called twice. The first call checks whether or not the property fname, which corresponds to the person’s first name, is a direct property of the object person. true is returned since fname is a direct property of person.

In the second call, the function checks whether or not the hasOwnProperty method belongs to the object person. Since it is an inherited property, the function returns false.

The return value is printed onto the console using the console.log function: