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JavaScript Bible, Gold Edition part 106

JavaScript Bible, Gold Edition part 106. 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. | 898 Part III Document Objects Reference Listing 31 -22 continued offsetY document.body.scrollTop return false function release evt evt evt evt window.event window.event var targElem evt.target evt.target evt.srcElement if targElem.className draggable while targElem.id myLayer targElem.parentNode targElem targElem.parentNode if engaged targElem.id myLayer engaged false SCRIPT HEAD BODY H1 Resizing a Layer W3C H1 HR DIV ID myLayer CLASS draggable STYLE position absolute top 170 left 100 width 300 height 190 background-color lightblue SPAN Here is some content inside the layer. See what happens to it as you resize the layer via the bottom-right 20-pixel handle. SPAN DIV SCRIPT LANGUAGE JavaScript document.onmousedown engage document.onmouseup release document.onmousemove resizelt document.onmouseout release SCRIPT BODY HTML This chapter only scratches the surface in the kinds of positioned element actions you can control via scripts. You may have seen examples of positioned element scripting at sites around the Web. For example some pages have subject headers fly into place even bounce around until they settle into position. Or elements can go in circles or spirals to get your attention or distract you as the case may be . The authors of those tricks apply formulas from other disciplines such as games programming to the style object properties of a positioned element. Chapter 31 PositionedObjects 899 Sometimes the effects are there just for the sake of looking at first anyway cool or because the page author knows how to script those effects. Your chief guide in implementing such features however should be whether the scripting genuinely adds value to the content offering. If you don t improve the content by adding a flying doo-dad or pulsating images then leave them out. A greater challenge is finding meaningful ways to apply positioning techniques. Done the right way and for the right reason they can significantly enhance the visitor s enjoyment of your application.