javascript

CHAPTER 7 ■ TRAVERSING AND MODIFYING THE DOM TREE
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Similarly, querying previousSibling on the first child node of the returns null, too:
var myUL = document.
childNodes[1].
childNodes[1].
childNodes[1].
childNodes[3];
myUL.childNodes[0].previousSibling;
// null
Now then, is there a simpler way to query the last child node of the than keying in
childNodes[myUL.childNodes.length - 1]? Oh, you betcha. Just query the aptly named lastChild
member:
var myUL = document.
childNodes[1].
childNodes[1].
childNodes[1].
childNodes[3];
myUL.lastChild.previousSibling;
//
Conversely, every kind of node has a firstChild member referring to its first child node. So rather
than querying childNodes[0], you can save a few keystrokes with firstChild. Note that, in addition to
saving keystrokes, lastChild and firstChild read better than their childNodes equivalents.
So, click Clear in both Firebug panels and give firstChild a try, verifying this and the previous
sample with Figure 7–7:
var myUL = document.
childNodes[1].
childNodes[1].
childNodes[1].
childNodes[3];
myUL.firstChild.nextSibling;
//