Campesato - JQuery Pocket Primer

jQuery
Pocket Primer

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jQuery
Pocket Primer

Oswald Campesato

Copyright 2015 by M ERCURY L EARNING AND I NFORMATION LLC. All rights reserved.

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O. Campesato. jQuery Pocket Primer.
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Id like to dedicate this book to my parents
may this bring joy and happiness into their lives.

This book endeavors to provide you with as much up-to-date information as possible regarding jQuery that can be reasonably included in a book consisting of roughly 200 pages. You need some familiarity with HTML Web pages and JavaScript, but no prior knowledge of jQuery is required.

Which Version of jQuery is for this Book?

The code samples in this book were initially written using jQuery 1.7.1. These code samples were upgraded to jQuery 2.0 beta, along with jQuery Migrate plugin (version 1.9.1) to ensure that the code samples do not contain any deprecated jQuery methods.

There are two benefits to this approach. First, you can use these HTML Web pages with jQuery 2.0 beta and be assured that they do not contain any deprecated jQuery code. In addition, if you need to use a version of jQuery prior to version 2.0 (perhaps due to an existing code base), these HTML Web pages work correctly without modification.

What About jQuery 2.0?

The current production version of jQuery is version 1.9, and jQuery 2.0 beta is also available. As this book goes to print, jQuery 2.0 will probably become available as well. The key point to remember is that jQuery 2.0 removes support for IE 6, IE 7, and IE 8, and also deprecates some jQuery methods that are available in earlier versions of jQuery. Fortunately, version 2.0 will be backward compliant with jQuery 1.9.

Which Version of jQuery Should Readers Use?

This is an important question because there are at least five active versions of jQuery in HTML Web pages (back to version 1.6.x). The answer is simple: strive to write code that is compliant with jQuery 2.0.

There are two things that you can do to achieve jQuery 2.0 compliance. First, make sure that you do not use the jQuery methods that have been desupported, which are available here (along with other changes):

http://jquery.com/upgrade-guide/1.9/

Second, use the jQuery Migrate plugin, which you can use with either 1.9 or 2.0 to detect deprecated and removed features, or to restore old features for cases where you need old code to run with new jQuery. The plugin and the messages it generates are documented in the project README.

You can use the plugin simply by including it after your jQuery file and check for warning messages regarding deprecated code. For example, if you plan to use jQuery 1.9 in your HTML Web pages, include the following code snippet:

If you plan to use jQuery 2.0 in your HTML Web pages, include the following code snippet:

When you add the preceding code snippet to an HTML Web page and then launch that Web page in a WebKit-based browser, you will see the following message in the Inspector if there are no errors:

JQMIGRATE: Logging is active

You can find additional details on the jQuery blog:

http://blog.jquery.com/

How Do I Actually Find the Deprecated Code?

Launch the HTML Web page in question in a WebKit-based browser and open the Web Inspector to check for errors or warnings. Unfortunately, the jQuery Migrate plugin can generate warning messages that are unintuitive. For example, consider the following code snippet in JQDragAndDrop1.html in Chapter 5: