Welcome!

Machine Learning Authors: Yeshim Deniz, Liz McMillan, Elizabeth White, Pat Romanski, Shelly Palmer

Related Topics: Java IoT, Microservices Expo, IBM Cloud, Weblogic, Machine Learning , 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>

Description

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() {
$(this).addClass("minus");
$(this).next().show();
},
function() {
$(this).removeClass("minus");
$(this).next().hide();
}
);  // 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>
</div>

The JavaScript code for the jQuery UI accordion

<script>
$(document).ready(function() {
$("#accordion").accordion();
});
</script>

Some typical plugin functions

ŸData validation

ŸSlide shows

ŸCarousels

Description
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.


@CloudExpo Stories
SYS-CON Events announced today that delaPlex will exhibit at SYS-CON's @ThingsExpo, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. delaPlex pioneered Software Development as a Service (SDaaS), which provides scalable resources to build, test, and deploy software. It’s a fast and more reliable way to develop a new product or expand your in-house team.
Most technology leaders, contemporary and from the hardware era, are reshaping their businesses to do software in the hope of capturing value in IoT. Although IoT is relatively new in the market, it has already gone through many promotional terms such as IoE, IoX, SDX, Edge/Fog, Mist Compute, etc. Ultimately, irrespective of the name, it is about deriving value from independent software assets participating in an ecosystem as one comprehensive solution.
SYS-CON Events announced today that Systena America will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Systena Group has been in business for various software development and verification in Japan, US, ASEAN, and China by utilizing the knowledge we gained from all types of device development for various industries including smartphones (Android/iOS), wireless communication, security technology and IoT serv...
Amazon started as an online bookseller 20 years ago. Since then, it has evolved into a technology juggernaut that has disrupted multiple markets and industries and touches many aspects of our lives. It is a relentless technology and business model innovator driving disruption throughout numerous ecosystems. Amazon’s AWS revenues alone are approaching $16B a year making it one of the largest IT companies in the world. With dominant offerings in Cloud, IoT, eCommerce, Big Data, AI, Digital Assista...
You know you need the cloud, but you’re hesitant to simply dump everything at Amazon since you know that not all workloads are suitable for cloud. You know that you want the kind of ease of use and scalability that you get with public cloud, but your applications are architected in a way that makes the public cloud a non-starter. You’re looking at private cloud solutions based on hyperconverged infrastructure, but you’re concerned with the limits inherent in those technologies.
SYS-CON Events announced today that Outscale will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Outscale's technology makes an automated and adaptable Cloud available to businesses, supporting them in the most complex IT projects while controlling their operational aspects. You boost your IT infrastructure's reactivity, with request responses that only take a few seconds.
Everywhere we turn in our industry we can find strong opinions about the direction, type and nature of cloud’s impact on computing and business. Another word that is used in every context in our industry is “hybrid.” In his session at 20th Cloud Expo, Alvaro Gonzalez, Director of Technical, Partner and Field Marketing at Peak 10, will use a combination of a few conceptual props and some research recently commissioned by Peak 10 to offer a real-world consideration of how the various categories of...
DevOps at Cloud Expo – being held October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA – announces that its Call for Papers is open. Born out of proven success in agile development, cloud computing, and process automation, DevOps is a macro trend you cannot afford to miss. From showcase success stories from early adopters and web-scale businesses, DevOps is expanding to organizations of all sizes, including the world's largest enterprises – and delivering real r...
Cloud applications are seeing a deluge of requests to support the exploding advanced analytics market. “Open analytics” is the emerging strategy to deliver that data through an open data access layer, in the cloud, to be directly consumed by external analytics tools and popular programming languages. An increasing number of data engineers and data scientists use a variety of platforms and advanced analytics languages such as SAS, R, Python and Java, as well as frameworks such as Hadoop and Spark...
Cloud promises the agility required by today’s digital businesses. As organizations adopt cloud based infrastructures and services, their IT resources become increasingly dynamic and hybrid in nature. Managing these require modern IT operations and tools. In his session at 20th Cloud Expo, Raj Sundaram, Senior Principal Product Manager at CA Technologies, will discuss how to modernize your IT operations in order to proactively manage your hybrid cloud and IT environments. He will be sharing bes...
Five years ago development was seen as a dead-end career, now it’s anything but – with an explosion in mobile and IoT initiatives increasing the demand for skilled engineers. But apart from having a ready supply of great coders, what constitutes true ‘DevOps Royalty’? It’ll be the ability to craft resilient architectures, supportability, security everywhere across the software lifecycle. In his keynote at @DevOpsSummit at 20th Cloud Expo, Jeffrey Scheaffer, GM and SVP, Continuous Delivery Busine...
Most DevOps journeys involve several phases of maturity. Research shows that the inflection point where organizations begin to see maximum value is when they implement tight integration deploying their code to their infrastructure. Success at this level is the last barrier to at-will deployment. Storage, for instance, is more capable than where we read and write data. In his session at @DevOpsSummit at 20th Cloud Expo, Josh Atwell, a Developer Advocate for NetApp, will discuss the role and value...
SYS-CON Events announced today that Outscale, a global pure play Infrastructure as a Service provider and strategic partner of Dassault Systèmes, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Founded in 2010, Outscale simplifies infrastructure complexities and boosts the business agility of its customers. Outscale delivers a secure, reliable and industrial strength solution for its customers, which in...
SYS-CON Events announced today that Peak 10, Inc., a national IT infrastructure and cloud services provider, will exhibit at SYS-CON's 20th International Cloud Expo®, which will take place on June 6-8, 2017, at the Javits Center in New York City, NY. Peak 10 provides reliable, tailored data center and network services, cloud and managed services. Its solutions are designed to scale and adapt to customers’ changing business needs, enabling them to lower costs, improve performance and focus intern...
SYS-CON Events announced today that CollabNet, a global leader in enterprise software development, release automation and DevOps solutions, will be a Bronze Sponsor of SYS-CON's 20th International Cloud Expo®, taking place from June 6-8, 2017, at the Javits Center in New York City, NY. CollabNet offers a broad range of solutions with the mission of helping modern organizations deliver quality software at speed. The company’s latest innovation, the DevOps Lifecycle Manager (DLM), supports Value S...
A strange thing is happening along the way to the Internet of Things, namely far too many devices to work with and manage. It has become clear that we'll need much higher efficiency user experiences that can allow us to more easily and scalably work with the thousands of devices that will soon be in each of our lives. Enter the conversational interface revolution, combining bots we can literally talk with, gesture to, and even direct with our thoughts, with embedded artificial intelligence, whic...
In order to meet the rapidly changing demands of today’s customers, companies are continually forced to redefine their business strategies in order to meet these needs, stay relevant and continue to see profitable growth. IoT deployment and development is integral in this transformation, and today businesses are increasingly seeing the value of investing their resources into IoT deployments. These technologies are able increase ROI through projects such as connecting supply chains or enabling sm...
Regardless of what business you’re in, it’s increasingly a software-driven business. Consumers’ rising expectations for connected digital and physical experiences are driving what some are calling the "Customer Experience Challenge.” In his session at @DevOpsSummit at 20th Cloud Expo, Marco Morales, Director of Global Solutions at CollabNet, will discuss how organizations are increasingly adopting a discipline of Value Stream Mapping to ensure that the software they are producing is poised to o...
This talk centers around how to automate best practices in a multi-/hybrid-cloud world based on our work with customers like GE, Discovery Communications and Fannie Mae. Today’s enterprises are reaping the benefits of cloud computing, but also discovering many risks and challenges. In the age of DevOps and the decentralization of IT, it’s easy to over-provision resources, forget that instances are running, or unintentionally expose vulnerabilities.
In his opening keynote at 20th Cloud Expo, Michael Maximilien, Research Scientist, Architect, and Engineer at IBM, will motivate why realizing the full potential of the cloud and social data requires artificial intelligence. By mixing Cloud Foundry and the rich set of Watson services, IBM's Bluemix is the best cloud operating system for enterprises today, providing rapid development and deployment of applications that can take advantage of the rich catalog of Watson services to help drive insigh...