This column introduces Version 4.0 of our cross-browser JavaScript and DHTML function library, DOCJSLIB. This version adds 18 new functions to the previous 3.1 version, which we have published in Column 29. The focus of this version is to support the HTML scroller we have shown in our previous column. If previous versions of DOCJSLIB focused on the <IMG> and <STYLE> tags, Version 4.0 concentrates on Netscape's <LAYER> and Internet Explorer's <DIV> DHTML tags.

You can benefit in two ways by using DOCJSLIB. First, you are spared from handling the differences between the browsers, as DOCJSLIB does it for you. Secondly, using DOCJSLIB will make your code shorter. Our cross-browser HTML scroller code squeezed from 180 lines to 118 lines, a reduction of 34%. The advantages of shorter code cannot be overemphasized. A shorter code is easier to debug, maintain, and explain to a friend how it works.

In this version we also switch to the overdue external JavaScript file implementation of DOCJSLIB. As you can see from this page, we have implemented two different features with DOCJSLIB: an HTML scroller at the upper right corner and a page watermark at the lower right corner. Both features use a common version of DOCJSLIB Version 4.0.

In this column you'll learn:

• How to distinguish between call-by-reference and call-by-string function calls.
• How to get an image's width, height, x, and y coordinates .
• How to get and set a DHTML element's height, width, top, and left coordinates.
• How to create a clipping region and set its visibility.
• How to move a DHTML element and how to redesign the HTML Scroller accordingly.
• How to streamline further the HTML scroller code.

At this point, you may also view the code for the Scroll Box and its control parameters, and the code for the Page Watermark. You can also view the code for the Connect-Three board game and even play it now. Finally, you can view the DOCJSLIB 4.0's code or download a zipped version of all these scripts.