Object Detection, Encapsulation, and Cross-Browser Objects
With the release of CSS and Netscapeâs Navigator 4.x, as well as Microsoftâs Internet Explorer 4.x, web-page developers could finally create sophisticated page effects such as animated page contents, collapsing menus, and in-page notifications. The only problem was that not all of the browsers used the same object model when providing this capability.
conditional statement. If the object doesnât exist, the condition
false. In Chapter 9, I
mentioned one object thatâs commonly used in older scripts:
document.all. Checking for
document.all can detect a browser that
supports the IE 4.x model. Another common object detection is to check
document.layers, which was
supported by Netscapeâs Navigator 4.x:
if (document.layers) ...
Luckily, all modern browsers support a fairly consistent model.
All support the
document.getElementById, which is critical
for accessing specific elements. All support the
style property (covered in the next
chapter), which allows you to change the CSS style properties of an