O'Reilly Releases "Learning JavaScript"

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Thursday, November 23, 2006; 07:14 AM

Revered by some for its capabilities and disdained by others for its simplicity, JavaScript has moved in and out of the limelight since its introduction in 1995. The recent flurry of enthusiasm for Ajax--Asynchronous JavaScript and XML--has brought JavaScript solidly into prominence once more: "The big word in web development now is Ajax," says Shelley Powers, author of Learning JavaScript (O'Reilly, US $29.99). "No matter what server-side language the developer is using or what they're building, at some point they're going to have to get their hands on JavaScript."

But if Ajax has helped popularize JavaScript, it's also complicated the language, Powers observes. "For some reason, JavaScript has developed a reputation for being an 'ugly' or less than useful language, and, as a consequence, Ajax developers have created libraries to make the language look more like Ruby or Python or even Java.

"However, they've also added all sorts of odd semantics into Ajax applications, with little documentation, and obscure references to items such as 'function closures' and so on," continues Powers. "So then you have JavaScript books and libraries that are focused on the old styles of web page development, and new Ajax libraries and books on the new style, and nothing bridges the two.

"This is where my book comes in," says Powers. "I've worked with and written about JavaScript as it's gone from mainly being an in-page method of manipulating forms to Dynamic HTML (DHTML) applications, and now Ajax. I've incorporated what I've learned through the years into an introduction to JavaScript that can also be considered a 'survival guide' to those learning JavaScript because they want to jump into Ajax."

Learning JavaScript provides web designers and programmers with an easy path through JavaScript's power and idiosyncrasies. Using web-based examples, Powers shows readers how to build JavaScript logic and connect it to existing object structures, as well as how to build libraries and take advantage of libraries others have written. The book also explores:

• Techniques for using JavaScript reliably in the multi-browser world of the web
• JavaScript's extensibility mechanisms and how they differ from 'traditional' object-oriented programming
• Handling traditional JavaScript tasks, such as form validation, DOM manipulation, and interactive styling
• JavaScript security, including the web-browser sandbox, cookies, and interaction with other objects
• Building Ajax applications with JavaScript and the XMLHttpRequest object
• Applying libraries for special effects and Ajax interactions

One of the most widely used languages available, JavaScript is also one of the most misunderstood. The reason for this, Powers explains, is that JavaScript is two languages in one. The first is a fast, friendly, easy-to-use scripting language built into web browsers and other applications, offering functions such as form validation, drop down menus, color fades during data updates, and in-place page edits. The second language, however, is a mature, full-featured, carefully constrained, object-based language, which does require more in-depth understanding.

"Used correctly," says Powers, "it can help web applications scale with little or no change to the application on the server. It can simplify website development and add a level of sophistication, making a good site appear even better to its visitors." Used incorrectly, she cautions, JavaScript can open security holes to a site or make a page unusable, unreadable, and less accessible.

In Learning JavaScript, Powers introduces readers to both languages: the fun scripting language and the powerful object-oriented programming language. "More importantly, I'm going to show you how to use JavaScript correctly," says Powers.