tailieunhanh - JavaScript Bible, Gold Edition part 9

JavaScript Bible, Gold Edition part 9. 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. | CD-10 Part II JavaScript Tutorial Proprietary and Standard Object Models Object model features that are proprietary to one browser version and or brand are perfectly usable provided you know that your audience uses that brand or version exclusively for example in a corporate environment where a browser version might be mandated for all employees . If you develop in this kind of controlled environment then be assured that browser-specific features are covered in the reference portions of this book. An industry standards effort by the W3C has begun specifying a common set of object model features and syntax that provide more flexibility than the original implementations. The biggest improvement is that every HTML element becomes an object that scripts can manipulate a feature also found in IE4 s object model . This DOM built upon the original object model you learn in this tutorial is implemented in varying degrees of completion in IE5 and NN6 the latter offering a much more complete W3C DOM implementation . The scripter s dream is that one day W3C DOM-compatible browsers will be the majority of the installed base and creating cross-browser highly dynamic pages will be easier than today. In the meantime you have lots of fundamentals to learn knowledge that you ll use for many years to come. Containment hierarchy Notice in Figure 4-6 that objects are grouped together in various levels designated by the density of the gray background. Objects are organized in a hierarchy not unlike the hierarchy of a company s organization chart of job positions. At the top is the president. Reporting to the president are several vice presidents. One of the vice presidents manages a sales force that is divided into geographical regions. Each region has a manager who reports to the vice president of sales each region then has several salespeople. If the president wants to communicate to a salesperson who handles a big account the protocol dictates that the president should route the .