Object-Oriented JavaScript

JavaScript uses functions as classes to create objects using the new keyword. Here is an example:

function Person(firstName, lastName) {
    // construct the object using the arguments
    this.firstName = firstName;
    this.lastName = lastName;

    // a method which returns the full name
    this.fullName = function() {
        return this.firstName + " " + this.lastName;
    }
}

var myPerson = new Person("John", "Smith");
print(myPerson.fullName());            // outputs "John Smith"

Creating an object using the new keyword is the same as writing the following code:

var myPerson = {
    firstName : "John",
    lastName : "Smith",
    fullName : function()
    {
        return this.firstName + " " + this.lastName;
    }
}

The difference between the two methods of creating objects is that the first method uses a class to define the object and then the new keyword to instantiate it, and the second method immediately creates an instance of the object.