With the help of examples, you will learn about JavaScript object methods and this keyword in this tutorial.

Objects in JavaScript can also contain functions. As an example:

// object containing method
const person = {
    name: 'John',
    greet: function() { console.log('hello'); }
};

In the preceding example, a person object has two keys (name and greet), each with a string value and a function value.

As a result, the JavaScript method is essentially an object property with a function value.

Accessing Object Methods

A dot notation is used to access an object method. The syntax is as follows:

objectName.methodKey()

You can get to a property by using an objectName and a key. You can call a method by providing an objectName and a key for that method (). As an example:

// accessing method and property
const person = {
    name: 'John',
    greet: function() { console.log('hello'); }
};

// accessing property
person.name; // John

// accessing method
person.greet(); // hello

In this case, the greet method is accessed as person.greet() rather than person.greet.

If you merely use person.greet to access the method, you will get a function definition.

person.greet; // ƒ () { console.log('hello'); }

JavaScript Built-In Methods

There are numerous built-in method in JavaScript. As an example:

let number = '23.32';
let result = parseInt(number);

console.log(result); // 23

The Number object’s parseInt() method is used here to convert a numeric string value to an integer value.

Adding a Method to a JavaScript Object

You can also add a method in an object. For example:

// creating an object
let student = { };

// adding a property
student.name = 'John';

// adding a method
student.greet = function() {
    console.log('hello');
}

// accessing a method
student.greet(); // hello

An empty student object is generated in the preceding example. The name property is then added. Similarly, the greet method is now available. You can add a method and a property to an object in this manner.

JavaScript this Keyword

To access an object’s property from within a method of the same object, use this keyword. Consider the following example.

const person = {
    name: 'John',
    age: 30,

    // accessing name property by using this.name
    greet: function() { console.log('The name is' + ' ' + this.name); }
};

person.greet();

Output

The name is John

• A person object is created in the preceding example. It has properties (name and age) and a greet method.
• This keyword is used in the greet method when accessing an object’s property.
• This keyword is used after. and key to access the properties of an object.

Note: When used with an object’s method in JavaScript, this keyword refers to the object. This is attached to an object.

However, a function within an object can access its variable in the same way that a normal function would. As an example:

const person = {
    name: 'John',
    age: 30,
    greet: function() {
        let surname = 'Doe';
        console.log('The name is' + ' ' + this.name + ' ' + surname); }
};

person.greet();

Output

The name is John

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