Head Rush Ajax

352

Chapter 6

So far, you’ve been using getElementById()

to nd a specic element in an HTML DOM

tree. But there’s another useful method called

getElementsByTagName(). You can use

this to nd all the elements in a DOM tree with a

certain name, like this:

I’m with you so far, but how can we get

to those three “sold” elements in the

XML? They don’t have id attributes like

the <span> elements in Katie’s HTML.

You can nd them with their “tag name”

var xmlDoc = request.responseXML;

var boardsSoldElements =

xmlDoc.getElementsByTagName(“boards-sold”);

This will return an array of all the elements

named “boards-sold” in the xmlDoc DOM tree.

Then, you can get elements from the list using an

index, like this:

var rstBoardsSoldElement =

boardsSoldElements[0];

Remember, JavaScript

arrays start at 0, not 1.

You could also loop through

this list using a “for” loop,

if you wanted to.

var rstBoardsSoldElement = xmlDoc.getElementsByTagName(“boards-sold”)[0];

Time to take a shortcut:

This gets all the elements

named “boards-sold”...

...and this returns just the

rst element from the list.

Get the DOM tree

representing the

server’s XML request.

Now we’re working

with the DOM!

working with xml using the dom

you’re on your way 4

353

xml requests and responses

If you use asynchronous requests in your JavaScript code, ...