tailieunhanh - JavaScript Bible, Gold Edition part 5

JavaScript Bible, Gold Edition part 5. This book will bring programmers and non-technical professionals, including casual programmers and scripters, painlessly up to speed on all aspects of mastering JavaScript. Key topics include programming fundamentals, JavaScript language elements and how to use them effectively, and how to easily and efficiently add powerful new functionality to HTML documents and Java applets. | 4 Part I Getting Started with JavaScript standards tools and other technologies at your disposal. The alternative technologies described in this chapter are HTML server programs plug-ins and Java applets. In most cases JavaScript can work side by side with these other technologies even though the hype around some make them sound like one-stop shopping places for all your interactive needs. That s rarely the case. Finally you learn about the origins of JavaScript and what role it plays in today s advanced Web browsers. Competition on the Web Web page publishers revel in logging as many visits to their sites as possible. Regardless of the questionable accuracy of Web page hit counts a site consistently logging 10 000 dubious hits per week is clearly far more popular than one with 1 000 dubious hits per week. Even if the precise number is unknown relative popularity is a valuable measure. Encouraging people to visit a site frequently is the Holy Grail of Web publishing. Competition for viewers is enormous. Not only is the Web like a ten million-channel television but the Web competes for viewers attention with all kinds of computergenerated information. That includes anything that appears onscreen as interactive multimedia. Users of entertainment programs multimedia encyclopedias and other colorful engaging and mouse finger-numbing actions are accustomed to high-quality presentations. Frequently these programs sport first-rate graphics animation live-action video and synchronized sound. In contrast the lowest common denominator Web page has little in the way of razzle-dazzle. Even with the help of recent advances in Dynamic HTML and style sheets the layout of pictures and text is highly constrained compared with the kinds of desktop publishing documents you see all the time. Regardless of the quality of its content a vanilla HTML document is flat. At best interaction is limited to whatever navigation the author offers in the way of hypertext links or forms whose .