MACROMEDIA DREAMWEAVER MX 2004-EXTENDING DREAMWEAVER Spécifications télécharger pdf (Page 127)

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CHAPTER 5

The Dreamweaver Document

Object Model

In Macromedia Dreamweaver 8, the Document Object Model (DOM) is a critically

important structure for extension builders. It lets you access and manipulate elements within a

user’s document and within the extension file.

A DOM defines the composition of documents that are created using a markup language. By

representing tags and attributes as objects and properties, the DOM lets programming

languages access and manipulate documents and their components.

The structure of an HTML document can be seen as a document tree. The root is the

HTML

tag, and the two largest trunks are the

HEAD tag and the BODY tag. Offshoots of the HEAD tag

include the

TITLE, STYLE, SCRIPT, ISINDEX, BASE, META, and LINK tags. Offshoots of the

BODY tag include headings (H1, H2, and so on), block-level elements (P, DIV, FORM, and so on),

text-level elements (

FONT, BR, IMG, and so on), and other element types. Leaves on these

offshoots include attributes such as

WIDTH, HEIGHT, ALT, and others.

In a DOM, the tree structure is preserved and presented as a hierarchy of parent nodes and

child nodes. The root node has no parent, and leaf nodes have no children. At each level

within the HTML structure, the HTML element can be exposed to JavaScript as a node.

Using this structure, you can access the document or any element within it.

In JavaScript, you can call any document object by name or by index, as described in the

following list:

■ By name, as in document.myForm.myButton

■ By index, as in document.forms[0].elements[1]

Objects with the same name are collapsed into an array. You can access a particular object in

the array by incrementing the index with zero as the origin (for example, the first radio button

with the name

myRadioGroup in the myForm document is referenced as

document.myForm.myRadioGroup[0]).

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