Java IoT Authors: Elizabeth White, TJ Randall, Hollis Tibbetts, Pat Romanski, Carmen Gonzalez

Related Topics: Java IoT, Microservices Expo, IBM Cloud, Weblogic, IoT User Interface, Apache

Java IoT: Article

Book Excerpt: jQuery Essentials | Part 1

An introduction to jQuery

This excerpt is from the book Murach's JavaScript and jQuery by Mike Murach and Zak Ruvalcaba.

Now that you have the JavaScript skills that you need for using jQuery, you're ready to learn jQuery. So, in this excerpt, you'll learn a working subset of jQuery that will get you off to a fast start.

When you complete this section, you'll have all the jQuery skills that you need for developing professional web pages. You can also go on to any of the three sections that follow because they are written as independent modules. If, for example, you want to learn how to use Ajax next, skip to section 4.

Get off to a fast start with jQuery
In this excerpt you'll quickly see how jQuery makes JavaScript programming easier. Then, you'll learn a working subset of jQuery that will get you off to a fast start. Along the way, you'll study four complete applications that will show you how to apply jQuery.

Introduction to jQuery
In this introduction, you'll learn what jQuery is, how to include it in your applications, and how jQuery, jQuery UI, and plugins can simplify JavaScript development.

What jQuery is
As Figure 1 summarizes, jQuery is a free, open-source, JavaScript library that provides dozens of methods for common web features that make JavaScript programming easier. Beyond that, the jQuery functions are coded and tested for cross-browser compatibility, so they will work in all browsers.

What jQuery offers

Dozens of methods that make it easier to add JavaScript features to your web pages

ŸMethods that are tested for cross-browser compatibility

How to include the jQuery file after you've downloaded it to your computer

<script src="jquery-1.8.2.min.js"></script>

How to include the jQuery file from a Content Delivery Network (CDN)

<script src="http://code.jquery.com/jquery-latest.min.js"></script>


ŸjQuery is a free, open-source, JavaScript library that provides methods that make JavaScript programming easier. Today, jQuery is used by more than 50% of the 10,000 most-visited web sites, and its popularity is growing rapidly.

ŸThe jQuery download comes in two versions. One version (min) is a compressed version that is relatively small and loads fast. The other version is uncompressed so you can use it to study the JavaScript code in the library.

ŸIf you include the jQuery file from a Content Delivery Network (CDN), you don't have to provide it from your own server, but then you can't work offline.

ŸThe jQuery CDN now provides a link that will always deliver the latest version of jQuery. That's the way the script element is coded in all of the applications in this book.

ŸIf you download the jQuery file to your system, you can change the filename so it's simpler, but then you may lose track of what version you're using.

Figure 1: What jQuery is and how to include it in your applications

Those are two of the reasons why jQuery is used by more than half of the 10,000 most-visited web sites today. And that's why jQuery is commonly used by professional web developers. In fact, you can think of jQuery as one of the four technologies that every web developer should know how to use: HTML, CSS, JavaScript, and jQuery. But don't forget that jQuery is actually JavaScript.

How to include jQuery in your web pages
If you go to the web site that's shown in this figure, you'll find a download button that lets you download the single file that contains the jQuery core library. By default, the version that's downloaded is a compressed version that today is around 32KB. As a result, this version loads quickly into browsers, which is another reason why developers like jQuery.

The other version is uncompressed and currently about 247KB. If you download this version, you can study the JavaScript code that's used in the library. But beware, this code is extremely complicated.

Once you've downloaded the compressed version of the core library, you can include it in a web page by coding a script statement like the first one in this figure. Then, if you store the file on your own computer or a local web server, you'll be able to develop jQuery applications without being connected to the Internet. For production applications, though, you'll need to deploy the file to your Internet web server.

In this script statement, the file name includes the version number, but you can use whatever file name you want. However, if the file name doesn't include the version number, it's easy to lose track of which version you're using.

The other way to include the jQuery library in your web applications and the one we recommend is to get the file from a Content Delivery Network (CDN). A CDN is a web server that hosts open-source software, and the Google, Microsoft, and jQuery web sites are CDNs for getting the jQuery libraries. In the second example in this figure, the script element uses the jQuery CDN with a URL that gets the latest version of jQuery, and that's the way all of the applications in this book include the jQuery library.

The benefit to using a CDN is that you don't have to download the jQuery file. This works especially well with the jQuery CDN and the "latest" URL. Then, you don't have to change the URL when a new release becomes available. The disadvantage is that you have to be connected to the Internet to use a CDN.

How jQuery can simplify JavaScript development
To show you how jQuery can simplify JavaScript development, Figure 2 shows both the JavaScript and the jQuery for the FAQs application that you learned how to develop in chapter 6. If you're like most people who are learning JavaScript, you probably found the JavaScript code for this application both complicated and confusing. That's because it is.

The JavaScript for the application

var $ = function (id) {
return document.getElementById(id);
window.onload = function () {
var faqs = $("faqs");
var h2Elements = faqs.getElementsByTagName("h2");
var h2Node;
for (var i = 0; i < h2Elements.length; i++ ) {
h2Node = h2Elements[i];
// Attach event handler
h2Node.onclick = function () {
var h2 = this;         // h2 is the current h2Node object
if (h2.getAttribute("class") == "plus") {
h2.setAttribute("class", "minus");   
else {
h2.setAttribute("class", "plus");
if (h2.nextElementSibling.getAttribute("class") == "closed") {
h2.nextElementSibling.setAttribute("class", "open");
else {
h2.nextElementSibling.setAttribute("class", "closed");

The jQuery for the application

$(document).ready(function() {
$("#faqs h2").toggle(
function() {
function() {
);  // end toggle
}); // end ready

Figure 2: How jQuery can simplify JavaScript development

In contrast, the jQuery code takes less than half as many lines of code. You'll also find that it is much easier to understand once you learn how to use the JQuery selectors, methods, and event methods. And you'll start learning those skills right after this introduction.

Incidentally, jQuery uses CSS selectors to select the HTML elements that the methods should be applied to. For instance,

$("#faqs h2")

is a jQuery selector for the CSS selector

#faqs h2

which selects all of the h2 elements in the element with "faqs" as its id. In fact, jQuery supports all of the CSS selectors including the CSS3 selectors, even in browsers that don't support all of the CSS3 selectors. This is another reason why developers like jQuery.

How jQuery can affect testing and debugging
When you use jQuery to develop applications, you can use the same testing and debugging skills that you learned in chapter 4. Remember, though, that a call to a jQuery method is a call to the jQuery file that you specify in a script element in the head section of the HTML. In other words, when your code executes a jQuery method, it is the JavaScript in the jQuery file that does the processing.

Then, if the jQuery code can't be executed, the display in Firebug or in the error console of the browser will point to a statement in the jQuery file. This can happen, for example, because a faulty parameter is passed to a jQuery method. Unfortunately, the information in Firebug or the error console doesn't tell you which statement in your code caused the problem. Instead, you have to use the other debugging techniques to find the bug and fix it.

In most cases, though, Firebug and the error console of the browser do provide information that helps you find and fix the bug. So this is a minor problem that is more than compensated for by the benefits that you get from using jQuery.

How jQuery UI and plugins can simplify JavaScript development
Besides the core jQuery library, jQuery provides the jQuery UI (User Interface) library. The functions in this library use the core jQuery library to build advanced features that can be created with just a few lines of code. These features include themes, effects, widgets, and mouse interactions.

For instance, the browser display in Figure 3 shows the FAQs application as a jQuery UI widget known as an accordion. To implement this widget, you just need the three lines of JavaScript code that are highlighted, and that also applies the formatting that's shown.

To use jQuery UI, you include a jQuery UI library file in your web pages in much the same way that you include the jQuery core library. You also include a jQuery UI CSS file that provides the themes for jQuery UI. In section 3, you'll learn how to do that, and you'll learn how to use the features of jQuery UI.

The HTML for a jQuery UI accordion

<div id="accordion">
<h3><a href="#">What is jQuery?</a></h3>
<div> <!-- panel contents --> </div>
<h3><a href="#">Why is jQuery becoming so popular?</a></h3>
<div> <!-- panel contents --> </div>
<h3><a href="#">Which is harder to learn: jQuery or JavaScript?></a></h3>
<div> <!-- panel contents --> </div>

The JavaScript code for the jQuery UI accordion

$(document).ready(function() {

Some typical plugin functions

ŸData validation

ŸSlide shows


jQuery UI is a free, open-source, JavaScript library that provides higher-level effects, widgets, and mouse interactions that can be customized by using themes. In section 3, you'll learn how to use jQuery UI.

A plugin is a JavaScript library that provides functions that work in conjunction with jQuery to make it easier to add features to your web applications. In chapter 11, you'll learn how to use some of the most useful plugins, and you'll also learn how to create your own plugins.

In general, if you can find a plugin or jQuery UI feature that does what you want it to do, you should use it. Often, though, you won't be able to find what you want so you'll need to develop the feature with just the core jQuery library.

Figure 3: How jQuery UI and plugins can simplify JavaScript development

Because jQuery UI can make JavaScript development even easier than it is when using jQuery, it makes sense to use jQuery UI whenever it provides an effect, widget, or mouse interaction that you need. Keep in mind, though, that jQuery UI is limited, so you'll still need jQuery for most of your web applications. As a result, you should think of jQuery UI as an add-on that you should learn how to use after you master jQuery.

Besides jQuery UI, the jQuery web site provides access to dozens of plugins that have been developed for jQuery. These plugins provide higher-level functions like data validation and drop-down menus that require minimal coding for their implementation. To facilitate the development of plugins, jQuery provides specifications that help standardize the way that plugins are implemented. Plugins are one more reason why developers like jQuery.

Like jQuery UI, plugins are libraries that make use of the core jQuery library. In fact, you can think of jQuery UI as a plugin. To use a plugin, you use a script element to include the plugin file in a web page, and you code that script element after the script element for the jQuery core library. In chapter 11, you'll learn how to get the most from plugins, and you'll also learn how to create your own plugins.

In practice, it makes sense to look first for a plugin that implements a feature that you want to add to a web page. If you can find one, you may be able to do in a few hours what would otherwise take a few days. Next, if you can't find a suitable plugin, it makes sense to see whether jQuery UI can facilitate the implementation of the feature. Finally, if neither a plugin nor jQuery UI can help you implement a feature, you have to use jQuery to develop it. That's why you need to master all of the jQuery skills in this section.

More Stories By Mike Murach

As a freelance writer many years ago, Mike Murach decided that he had to develop his own writing methods because the ones that others were using clearly didn’t work. Since then, Mike and his staff have continued to refine those methods, so today every Murach book becomes the best one on its subject. Now, after a long hiatus from writing, Mike has teamed with Zak Ruvalcaba to write Murach’s JavaScript and jQuery.

More Stories By Zak Ruvalcaba

Zak Ruvalcaba has been researching, designing, and developing for the Web since 1995. He holds a BS from San Diego State University and an MS in instructional technology from National University in San Diego.

Zak's skillset includes HTML/HTML5, CSS/CSS3, JavaScript, jQuery, ASP.NET, ADO.NET, Visual Basic, C#, Web Services, and Flash/ActionScript. He is also a Microsoft Certified Application Developer for .NET (MCAD) and a Microsoft Certified Solutions Developer for .NET (MCSD).

In his spare time, Zak teaches web development courses for the San Diego Community College District, Mt. San Jacinto Community College and Palomar Community College.

Comments (0)

Share your thoughts on this story.

Add your comment
You must be signed in to add a comment. Sign-in | Register

In accordance with our Comment Policy, we encourage comments that are on topic, relevant and to-the-point. We will remove comments that include profanity, personal attacks, racial slurs, threats of violence, or other inappropriate material that violates our Terms and Conditions, and will block users who make repeated violations. We ask all readers to expect diversity of opinion and to treat one another with dignity and respect.

@ThingsExpo Stories
In the next five to ten years, millions, if not billions of things will become smarter. This smartness goes beyond connected things in our homes like the fridge, thermostat and fancy lighting, and into heavily regulated industries including aerospace, pharmaceutical/medical devices and energy. “Smartness” will embed itself within individual products that are part of our daily lives. We will engage with smart products - learning from them, informing them, and communicating with them. Smart produc...
SYS-CON Events announced today that 910Telecom will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Housed in the classic Denver Gas & Electric Building, 910 15th St., 910Telecom is a carrier-neutral telecom hotel located in the heart of Denver. Adjacent to CenturyLink, AT&T, and Denver Main, 910Telecom offers connectivity to all major carriers, Internet service providers, Internet backbones and ...
SYS-CON Events announced today that Coalfire will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Coalfire is the trusted leader in cybersecurity risk management and compliance services. Coalfire integrates advisory and technical assessments and recommendations to the corporate directors, executives, boards, and IT organizations for global brands and organizations in the technology, cloud, health...
SYS-CON Events announced today that Transparent Cloud Computing (T-Cloud) Consortium will exhibit at the 19th International Cloud Expo®, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. The Transparent Cloud Computing Consortium (T-Cloud Consortium) will conduct research activities into changes in the computing model as a result of collaboration between "device" and "cloud" and the creation of new value and markets through organic data proces...
The Internet of Things (IoT), in all its myriad manifestations, has great potential. Much of that potential comes from the evolving data management and analytic (DMA) technologies and processes that allow us to gain insight from all of the IoT data that can be generated and gathered. This potential may never be met as those data sets are tied to specific industry verticals and single markets, with no clear way to use IoT data and sensor analytics to fulfill the hype being given the IoT today.
WebRTC defines no default signaling protocol, causing fragmentation between WebRTC silos. SIP and XMPP provide possibilities, but come with considerable complexity and are not designed for use in a web environment. In his session at @ThingsExpo, Matthew Hodgson, technical co-founder of the Matrix.org, discussed how Matrix is a new non-profit Open Source Project that defines both a new HTTP-based standard for VoIP & IM signaling and provides reference implementations.
In his general session at 18th Cloud Expo, Lee Atchison, Principal Cloud Architect and Advocate at New Relic, discussed cloud as a ‘better data center’ and how it adds new capacity (faster) and improves application availability (redundancy). The cloud is a ‘Dynamic Tool for Dynamic Apps’ and resource allocation is an integral part of your application architecture, so use only the resources you need and allocate /de-allocate resources on the fly.
We're entering the post-smartphone era, where wearable gadgets from watches and fitness bands to glasses and health aids will power the next technological revolution. With mass adoption of wearable devices comes a new data ecosystem that must be protected. Wearables open new pathways that facilitate the tracking, sharing and storing of consumers’ personal health, location and daily activity data. Consumers have some idea of the data these devices capture, but most don’t realize how revealing and...
A completely new computing platform is on the horizon. They’re called Microservers by some, ARM Servers by others, and sometimes even ARM-based Servers. No matter what you call them, Microservers will have a huge impact on the data center and on server computing in general. Although few people are familiar with Microservers today, their impact will be felt very soon. This is a new category of computing platform that is available today and is predicted to have triple-digit growth rates for some ...
SYS-CON Events announced today that MathFreeOn will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. MathFreeOn is Software as a Service (SaaS) used in Engineering and Math education. Write scripts and solve math problems online. MathFreeOn provides online courses for beginners or amateurs who have difficulties in writing scripts. In accordance with various mathematical topics, there are more tha...
In past @ThingsExpo presentations, Joseph di Paolantonio has explored how various Internet of Things (IoT) and data management and analytics (DMA) solution spaces will come together as sensor analytics ecosystems. This year, in his session at @ThingsExpo, Joseph di Paolantonio from DataArchon, will be adding the numerous Transportation areas, from autonomous vehicles to “Uber for containers.” While IoT data in any one area of Transportation will have a huge impact in that area, combining sensor...
SYS-CON Events announced today that SoftNet Solutions will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. SoftNet Solutions specializes in Enterprise Solutions for Hadoop and Big Data. It offers customers the most open, robust, and value-conscious portfolio of solutions, services, and tools for the shortest route to success with Big Data. The unique differentiator is the ability to architect and ...
The best way to leverage your Cloud Expo presence as a sponsor and exhibitor is to plan your news announcements around our events. The press covering Cloud Expo and @ThingsExpo will have access to these releases and will amplify your news announcements. More than two dozen Cloud companies either set deals at our shows or have announced their mergers and acquisitions at Cloud Expo. Product announcements during our show provide your company with the most reach through our targeted audiences.
More and more brands have jumped on the IoT bandwagon. We have an excess of wearables – activity trackers, smartwatches, smart glasses and sneakers, and more that track seemingly endless datapoints. However, most consumers have no idea what “IoT” means. Creating more wearables that track data shouldn't be the aim of brands; delivering meaningful, tangible relevance to their users should be. We're in a period in which the IoT pendulum is still swinging. Initially, it swung toward "smart for smar...
@ThingsExpo has been named the Top 5 Most Influential Internet of Things Brand by Onalytica in the ‘The Internet of Things Landscape 2015: Top 100 Individuals and Brands.' Onalytica analyzed Twitter conversations around the #IoT debate to uncover the most influential brands and individuals driving the conversation. Onalytica captured data from 56,224 users. The PageRank based methodology they use to extract influencers on a particular topic (tweets mentioning #InternetofThings or #IoT in this ...
SYS-CON Events announced today that Niagara Networks will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Niagara Networks offers the highest port-density systems, and the most complete Next-Generation Network Visibility systems including Network Packet Brokers, Bypass Switches, and Network TAPs.
In an era of historic innovation fueled by unprecedented access to data and technology, the low cost and risk of entering new markets has leveled the playing field for business. Today, any ambitious innovator can easily introduce a new application or product that can reinvent business models and transform the client experience. In their Day 2 Keynote at 19th Cloud Expo, Mercer Rowe, IBM Vice President of Strategic Alliances, and Raejeanne Skillern, Intel Vice President of Data Center Group and ...
Data is the fuel that drives the machine learning algorithmic engines and ultimately provides the business value. In his session at Cloud Expo, Ed Featherston, a director and senior enterprise architect at Collaborative Consulting, will discuss the key considerations around quality, volume, timeliness, and pedigree that must be dealt with in order to properly fuel that engine.
Virgil consists of an open-source encryption library, which implements Cryptographic Message Syntax (CMS) and Elliptic Curve Integrated Encryption Scheme (ECIES) (including RSA schema), a Key Management API, and a cloud-based Key Management Service (Virgil Keys). The Virgil Keys Service consists of a public key service and a private key escrow service. 

Fact is, enterprises have significant legacy voice infrastructure that’s costly to replace with pure IP solutions. How can we bring this analog infrastructure into our shiny new cloud applications? There are proven methods to bind both legacy voice applications and traditional PSTN audio into cloud-based applications and services at a carrier scale. Some of the most successful implementations leverage WebRTC, WebSockets, SIP and other open source technologies. In his session at @ThingsExpo, Da...