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Chapter 7
Document Element Collections
The Dynamic HTML object model represents the document's
structure through a set of collections exposed on the
document object. These collections provide access
to all HTML elements contained within the document. Understanding how these
collections relate to the HTML source code and how to access these collections is
the first step to programming the HTML document. This chapter shows you how
to manipulate the document element collections as well as how Microsoft
Internet Explorer 4.0 parses the document.
Consider the following short HTML document:
<HTML>
<HEAD>
<TITLE>Document Structure</TITLE>
</HEAD>
<BODY>
<H1>Overview</H1>
<P>Examining an HTML document</P>
</BODY>
</HTML>
The object model provides a way to access the HTML, Head, Title, Body, H1,
and Paragraph elements and thereby modify their attributes. The markup, like all
aspects of the document, is accessed using the document
object introduced in Chapter 6, "The HTML Document." The
document object exposes an all collection that
represents every element in the document and several filtered collections that
represent a subset of the document's elements. For example, the
forms collection contains only the Form elements. In addition, developers can create their own custom
collections of document elements.
The ability to access any element in the document is a key innovation
in Dynamic HTML. Until Dynamic HTML, scripts could manipulate only the set
of elements deemed interesting by vendors developing the browsers. Now Web
developers have complete control over the page and can decide for themselves what
is interesting. They can filter the all collection and manipulate any set of elements
as a group, removing all limitations and providing universal access to the document.
The following topics are covered in this chapter:
- Using the collections Every collection in Dynamic HTML shares the same set of operations. This section shows you how to access the elements within each collection, as well as how to create custom
collections of elements. Because every collection in the HTML object model follows the same rules, this section provides a solid basis for manipulating and using the collections. The rest of Part II builds on this information by showing you how to manipulate the individual elements within the collections.
- The HTML structure and collections This section describes how the HTML document is parsed and exposed by the underlying
collections. This discussion also covers how invalid HTML documents are
parsed and surfaced in the object model, which is important to
understand when you are scripting generic pages in which control over
the document's structure is not available.
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