Programming html5 applications ebook

It also makes the Web a first-class development environment by giving JavaScript programmers a solid foundation for building industrial-strength applications.

This practical guide takes you beyond simple site creation and shows you how to build self-contained HTML5 applications that can run on mobile devices and compete with desktop apps. Complete with code samples, this book is ideal for experienced JavaScript and mobile developers alike. Programming HTML5 Applications provides the knowledge to guide you through all the new technologies needed to make modern web applications.

Learn algorithms for solving classic computer science problems with this concise guide covering everything from fundamental …. Distributed systems have become more fine-grained as organizations shift from code-heavy monolithic applications to smaller, self-contained ….

Upload eBook. Privacy Policy. New eBooks. Search Engine. HTML5 is not just a replacement for plugins. It also makes the Web a first-class development environment by giving JavaScript programmers a solid foundation for building industrial-strength applications.

This practical guide takes you beyond simple site creation and shows you how to build self-contained HTML5 applications that can run on mobile devices and compete with desktop apps.

You'll learn powerful JavaScript tools for exploiting HTML5 elements, and discover new methods for working with data, such as offline storage and multithreaded processing. Using ExtJS or jQuery, it is possible to build an app that for many users can rival what can be done in a desktop application, and provide a method of distribution that is about as simple as it gets.

But however nice the browser has been in terms of providing a user experience, it has fallen flat when it comes to data storage. Historically, browsers did not have any way to store data. They were, in effect, the ultimate thin client. However, cookies suffer from several problems. First, each cookie is sent back and forth with every request. So the browser sends the cookie for each JavaScript file, image, Ajax request, and so on.

This can add a lot of bandwidth use for no good reason. Second, the cookie specification tried to make it so that a cookie could be shared among different subdomains. If a company had app. The problem with this is that outside of the United States, three-part domain names become common.

For example, it would be possible to set a cookie for all the hosts in. And it is not possible to simply require a three-part domain name whenever the name contains a country suffix, because some countries such as Canada do not follow the same convention. Having local storage on the browser can be a major advantage in terms of speed.

A normal Ajax query can take anywhere from half a second to several seconds to execute, depending on the server. However, even in the best possible case it can be quite slow. Of that ms, a large part is probably due to basic physical limitations: data can travel down the wire at just some fraction of the speed of light. So there is very little that can be done to make that go faster, as long as the data has to travel between browser and server.

Local storage options are a very good option for data that is static or mostly static. For example, many applications have a list of countries as part of their data. Even if the list includes some extra information, such as whether a product is being offered in each country, the list will not change very often. In this case, it often works to have the data preloaded into a localStorage object, and then do a conditional reload when necessary so that the user will get any fresh data, but not have to wait for the current data.

Local storage is, of course, also essential for working with a web application that may be offline. Although Internet access may seem to be everywhere these days, it should not be regarded as universal, even on smartphones.

Users with devices such as the iPod touch will have access to the Internet only where there is WiFi, and even smartphones like the iPhone or Android will have dead zones where there is no access. With the development of HTML5, a serious movement has grown to provide the browser with a way to create persistent local storage, but the results of this movement have yet to gel. There are currently at least three different proposals for how to store data on the client.

The localStorage mechanism provides a JavaScript object that persists across web reloads. This mechanism seems to be reasonably well agreed on and stable. It is good for storing small-sized data such as session information or user preferences. This current chapter explains how to use current localStorage implementations.

Modern browsers provide two objects to the programmer for storage, localStorage and sessionStorage. Each can hold data as keys and values.

They have the same interface and work in the same way, with one exception. The localStorage object is persistent across browser restarts, while the sessionStorage object resets itself when a browser session restarts. This can be when the browser closes or a window closes. Exactly when this happens will depend on the specifics of the browser. Setting and getting these objects is pretty simple, as shown in Example Cookies are burdened with certain restrictions: they are limited to about 4 KB in size and must be transmitted to the server with every Ajax request, greatly increasing network traffic.

The HTML5 specification does not list an exact size limit for its size, but most browsers seem to limit it to about 5 MB per web host. The programmer should not assume a very large storage area. Data can be stored in a storage object with direct object access or with a set of access functions. The session object can store only strings, so any object stored will be typecast to a string. This means an object will be stored as [object Object] , which is probably not what you want.

To store an object or array, convert it to JSON first. Whenever a value in a storage object is changed, it fires a storage event. This event will show the key, its old value, and its new value. A typical data structure is shown in Example Unlike some events, such as clicks, storage events cannot be prevented.

There is no way for the application to tell the browser to not make a change. The event simply informs the application of the change after the fact.