tailieunhanh - JavaScript Bible, Gold Edition part 75

JavaScript Bible, Gold Edition part 75. 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. | Select Option and FileUpload Objects election lists whether in the form of pop-up menus or scrolling lists are space-saving form elements in HTML pages. They enable designers to present a lot of information in a comparatively small space. At the same time users are familiar with the interface elements from working in their own operating systems preference dialog boxes and application windows. However selection lists are more difficult to script especially in older browsers because the objects themselves are complicated entities. Scripts find all the real data associated with the form control in OPTION elements that are nested inside SELECT elements. As you can see throughout this chapter backward-compatible references necessary to extract information from a SELECT element object and its OPTION objects can get pretty long. The results however are worth the effort. The other object covered in this chapter the fileUpload input object is frequently misunderstood as being more powerful than it actually is. It is alas not the great file transfer elixir desired by many page authors. SELECT Element Object For HTML element properties methods and event handlers see Chapter 15. In This Chapter Triggering action based on a user s selection in a pop-up or select list Modifying the contents of SELECT objects Using the fileUpload object 590 Part III Document Objects Reference Properties Methods Event Handlers formt options i .add onChange length item multiple namedItem namet options i .remove options selectedIndex size type value fSee text input object Chapter 25 . Syntax Accessing SELECT element object properties All window. method parameters All window. index .property method parameters All window. index . method parameters All window. formName . method parameters All window. formName .elements index .property method parameters IE4