JavaScript

JavaScript is a subset of DHTML. {DHTML stands for dynamic HTML. DHTML is composed of 3 technologies - 1) standard HTML, 2) JavaScript, and 3) Cascading Styles Sheets (CSS) }. One advantage of using Javascript is since all the processing takes place on each vistor's own browser, it frees up the host server from otherwise needing to perform the same calcualtions for each visitor. And certain functionalities can only be accomplished via JavaScript. However, a big disadvantage to JavaScript is that it is not inherently very cross-browser and cross-platform compatible. That means that the same JavaScript code which works perfectly on a Windows XP machine using an Internet Explorer browser, may work poorly (or not at all) on a Macintosh machine running the same version of Internet Explorer. Further, even on the same Operating System, it may not work on other browsers (such as Mozilla Firefox and/or Netscape). One big difference between browsers like Internet Explorer and Firefox, is that they each have a significantly different DOM (Document Object Model). That means that some JavaScript code which is supported on one, either may not be supported on the other at all, or even if it is, it may need to be handled differently. Because of these incompatibilites, I often have to write extra code that first attempts to check to see what platform, OS, browser and version the visitor is using, and depending on that test result, then load different versions of JavaScript code that should best work on that person's particular system. But since there are nearly an infinite number of permutations of platform, OS, browser and version, it is virtually impossible to guarantee it will operate properly on 100 percent of the vistor's computers. The best you can reasonably strive for, and realistically hope to achieve, is proper desired operation for 98-99 percent of all visitors.

However, in spite of the above limitations, using JavaScript is essential to many web pages in use today. A good manual coder should be able to ensure desirable JavaScript operation for over 95 percent of the website's visitors. So using JavaScript, together with CSS and of course standard HTML, websites achieve very robust capabilities while simultaneously looking more appealing than the average plain HTML websites.