This chapter's recipes
attempt to provide solutions for real-world challenges that you may
encounter in your DHTML development. The difficulty in arriving at
such a roster of solutions is that DHTML is flexible enough to
inspire the imaginations of every developer in different directions.
While most of the recipes here can be used as-is, they are also meant
to serve as basic foundations upon which you can build your specific
application. If these recipes give you ideas for ways to add value to
your site, all the better.
Several of the recipes in this chapter rely on scriptable objects
language Date object (covered in depth in Chapter 2), and an object representing text ranges
(known as the TextRange object in IE for Windows
and the Range object in the W3C DOM). The abstract
nature of these objects and the technical details of their operation
can cause numerous conceptual problems along the way.
Although the details of text range implementations in the IE for
Windows and W3C DOMs are quite different, their fundamental
operations are the same. At its core, a text
is a sequence of body text separate from the HTML elements that
surround or are nested within the sequence. You
don't see a text range, per se, although it is
possible to highlight its text for the user to see, if
it's important to your application.
A text range has a starting point and an ending point. When you
create a text range, it has a default set of boundaries (again, the
details vary with DOM type). Relocating those two boundaries may
entail a reference to an HTML element, but the text range itself is
devoid of any node hierarchy like that of the HTML document. The
typical sequence of working with a text range is to create the
abstract text range, position its boundary points, and then perform
some operation on the text (such as removing the contents or grabbing
a copy of the text). For example, you can convert a user selection of
a portion of body text to a span element that is
then under the control of a style sheet rule (see Recipe 15.2).
Between the two implementations, the IE
TextRange object is the more flexible and better
equipped for practical duty. It is the only one that offers
facilities for searching within the body text for string matches (and
positioning the boundary points around the found instance).
Importantly, the IE TextRange object can also be
applied to content in a textarea element.
Therefore, while it may appear cool to be able to script a global
search-and-replace operation in the body text (Recipe 15.3),
it's more practical in a textarea
containing a bunch of text supplied by the user. Of course, IE 5.5 or
later for Windows offers facilities in the browser to make the body
content editable (although you must still provide a server mechanism
for preserving the changes).
Because many of the recipes in this chapter deal with positioning
elements on the page, many rely on the importation of the DHTML API
library shown in Recipe 13.3. Scripts with dependencies on the
functions of that library are clearly marked. Although the library is
not large, you are free to create a version of the library that
includes only the functions needed for a specific application. Or you
can copy and paste those functions into your in-document code or
other .js library code. Also, be on the lookout
for recipes that employ cookies to preserve settings across
settings—they use the cookies.js library
from Recipe 1.9.