Introduction • “Today, Java. Script is used on most of the pages of a modern website, from small individual sites to the largest commercial sites. And wherever Java. Script is used, you’ll find j. Query. That’s because j. Query is a Java. Script library that makes it easier to develop Java. Script applications. And that’s why every web developer should know how to use both Java. Script and j. Query, right along with HTML 5 and CSS 3. ”