Training Guide: Programming in HTML5 with JavaScript and CSS3 Ebook

266 CHAPTER 6 Essential JavaScript and jQuery

After the object is created, you can dynamically add properties to it that hold the data and

reference functions. You can wrap this code in a function that returns the object as shown in

the following code example.

function getVehicle(theYear, theMake, theModel) {

var vehicle = new Object();

vehicle.year = theYear;

vehicle.make = theMake;

vehicle.model = theModel;

vehicle.getInfo = function () {

return 'Vehicle: ' + this.year + ' ' + this.make + ' ' + this.model;

};

return vehicle;

}

This code takes advantage of JavaScript’s dynamic nature to add year, make, model, and

getInfo to the object and then returns the object. Placing this code in a function makes it easy

to call the getVehicle function to get a new object. The encapsulation of the code to create an

object is commonly referred to as using the factory pattern. Can you create multiple instances

of vehicle? You can create multiple instances of Object and add properties dynamically to

each instance, but the actual type is Object, not vehicle. The following QUnit test demon-

strates the creation of multiple instances.

test("Create Instances Test Using Factory Pattern", function () {

expect(2);

var car1 = getVehicle(2000, 'Ford', 'Fusion');

var car2 = getVehicle(2010, 'BMW', 'Z4');

var expected = 'Vehicle: 2000 Ford Fusion';

var actual = car1.getInfo();

equal(actual, expected, 'Expected value: ' + expected +

' Actual value: ' + actual);

var expected = 'Vehicle: 2010 BMW Z4';

var actual = car2.getInfo();

equal(actual, expected, 'Expected value: ' + expected +

' Actual value: ' + actual);

});

This might be all you need when you are gathering some data to put into an object struc-

ture and pass to some other code or service. Although the getVehicle function encapsulates

the object creation, the properties are all public. This can be desirable in some scenarios, but

if you want the data to be private, this approach won’t work. Like when using the literal object

syntax, you might encounter the problem that every vehicle’s type is Object, and you might

want to create a Vehicle class to have a named Vehicle type.

Creating a class

There is no class keyword in JavaScript, but you can simulate a class by starting with a func-

tion, which is actually the constructor function of the object. Consider the following function.

function Vehicle(theYear, theMake, theModel) {

year = theYear;

Key

Te rms