Head Rush Ajax

you’re on your way �

223

the document object model

OK, I get all this business about a web

browser seeing my pages as trees... but

how does that really help me? I need to

change a web page, not grow one.

See? If you want to understand web

pages, you have to master trees.

Mike: Often, the root must be watered carefully

before one can enjoy the leaf.

Jenny: What the heck does that mean?

Mike: Honestly, I have no idea. I read it somewhere,

and thought that it might impress you. Anyway... since

web browsers view your pages as trees, you need to be

able to write code that works on those trees. And that’s

where the Document Object Model comes in.

Jenny: OK, now we’re talking. That’s what I came

here to nd out about... the Document Object Model.

Mike: The Document Object Model—usually called

the DOM for short—is how you can work on the tree

that the browser creates from your web page. You can

manipulate the DOM with JavaScript, and update the

browser’s tree. And once you update the tree, the page

itself will automatically be changed by the browser,

without any page reloading or refreshing.

There’s a group called the

World Wide Web Consortium

(most people call them

the W3C for short) that

publishes the specications

and standards for the DOM.

Just a bit of trivia for you

standards gurus out there...