Web Standards Programmer's Reference: HTML, CSS, JavaScript®, Perl, Python®, and PHP

21.1. The History of the DOM

The Document Object Model was developed by the World Wide Web Consortium (W3C) to allow programming languages access to the underlying structure of a Web document. Using the DOM a program can access any element in the document, determining and changing attributes and even removing, adding, or rearranging elements at will.

It's important to note that the DOM is a type of application program interface (API) allowing any programming language access to the structure of a Web document. The main advantage of using the DOM is the ability to manipulate a document without another trip to the document's server. As such, the DOM is typically accessed and used by client-side technologies, such as JavaScript. Therefore, the coverage of the DOM in this book appears in the JavaScript part of the book and is very JavaScript-centric.

The first DOM specification (Level 0) was developed at the same time as JavaScript and early browsers. It is supported by Netscape 2 onward.

There were two intermediate DOMs supported by Netscape 4 onward and Microsoft Internet Explorer (IE) versions 4 and 5 onward. These DOMs were proprietary to the two sides of the browser coin — Netscape and Microsoft IE. The former used a collection of elements referenced through a document.layers object, while the latter used a document.all object. To be truly cross-browser compatible, a script should endeavor to cover both of these DOMs instead of one or the other.

Techniques for accessing these ...