Page 169 - DCAP202_Fundamentals of Web Programming

Fundamentals of Web Programming

Notes 14.1 DHTML Basic

DHTML is not a language itself, but rather a combination of:
 HTML 4.0 (or XHTML 1.0)

 JavaScript — the Web’s standard scripting language
 Cascading Style Sheets (CSS) — styles dictated outside a document’s content
 Document Object Model (DOM) — a means of accessing a document’s individual elements
Dynamic HTML (DHTML) is a set of innovative features originally introduced in Microsoft
Internet Explorer 4.0. By enabling authors to dynamically change the rendering and content of
a Web page as the user interacts with it, DHTML enables authors to create visually compelling
Web sites without the overhead of server-side programs or complicated sets of controls to
achieve special effects.
With DHTML, you can easily add effects to your pages that previously were difficult to achieve.

Example: you can:
 Hide content until a given time elapses or the user interacts with the page.
 Animate text and images in your document, independently moving each element
from any starting point to any ending point, following a predetermined path or one
chosen by the user.
 Embed a ticker that automatically refreshes its content with the latest news, stock
quotes, or other data.
 Use a form to capture user input, and then instantly process and respond to that data.
DHTML achieves these effects by modifying the in-memory representation of the current
document and automatically reformatting it to show changes. It does not reload the document,
load a new document, or require a distant server to generate new content. Instead, it uses the
user’s computer to calculate and carry out changes. This means a user does not wait for text and
data to complete time-consuming round trips to and from a server before seeing the results.
Furthermore, DHTML does not require additional support from applications or embedded
controls to make changes. Typically, DHTML documents are self-contained, using styles and a
script to process user input and directly manipulate the HTML elements, attributes, styles, and
text of the document.

Notes In short, DHTML eliminates the shortcomings of static pages. You can create
innovative Web sites, on the Internet or on an intranet, without having to sacrifice
performance for interactivity. Not only does DHTML enhance the user’s perception of
your documents, it also improves server performance by reducing requests to the server.

14.1.1 DHTML Technologies

Speaking in true sense there is nothing dynamic in DHTML but enclosing technologies such as
CSS, JavaScript, DOM and the static markup language it becomes dynamic.
JavaScript: Whether we call it JavaScript, Jscript, or ECMAScript, it is the most common language
used today for client-side scripting. The main reason for this JavaScript comes with virtually
every browser.

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