Head Rush Ajax

you’re on your way �

233

the document object model

Sweet! Now I can nd any element I want, move up

and down the DOM tree... I’ll bet I can get element

names and text values, too, right?

Remember, everything in a DOM tree is a node.

Elements and text are special kinds of nodes, but

they’re still nodes. Anytime you have a node, you

can get the name of the node with nodeName,

and the value of the node with nodeValue.

You’ve got to be careful what type of node you’re

working on, though, or you could end up getting

a null value when you’re expecting the name

of an element or a string of text. An element

node has a name, like “div” or “img”, but won’t

have a value. And a text node won’t have a

name, but it will have a value: the actual text

stored in the node.

Let’s take a look and see how this works:

The node knows... pretty much everything.

“breadth-rst”

em

div

nodeName

nodeValue

“div”

null/undened

“breadth-rst”

The nodeValue for an

element node is undened.

The nodeValue

of a text node

is its text.

Element nodes all

have a nodeName.

Text nodes do not

have a nodeName.

node type

node

element

node

“em”

null/undened

element

node

null/undenedtext node

234

Chapter 4

You’ve got to keep up with what type of node you’re working on, and always know where

in the DOM tree your variables are pointing. To help you get ...