Summary

Microsoft implements its own version of JavaScript called JScript. While the different versions of JScript included in Internet Explorer correspond in varying degrees to versions of Netscape JavaScript, Microsoft has come in line with many standards. JScript 3.0 is compliant with ECMAScript Edition 1 and JScript 5.5 is compliant with ECMAScript Edition 3. However, Microsoft JScript does offer several proprietary features not found in other browsers. For example, conditional compilation allows pieces of code to be selectively included or excluded depending upon platform and JScript version information.

Aside from its proprietary Document Object Model, Internet Explorer comes equipped with a variety of useful features not found in other browsers. Data Binding allows data sources such as SQL databases to be bound to HTML elements and data records to be manipulated with JScript. Dynamic Properties expand the type of values to which document object properties can be set to include expressions that are evaluated dynamically. HTML Applications are HTML documents run as fully trusted applications on the client machine and have access to the full features of the user’s operating system. DHTML Behaviors is a powerful technology that allows the encapsulation of specific DHTML functionality into reusable HTML components that can be bound to elements in the page in a variety of ways.

Although Internet Explorer provides a wealth of proprietary features, whether these features should be used in a Web site is an important question. Doing so prevents users on non-Windows platforms or with other browsers from using your pages. From a usability perspective, it is highly desirable to include equivalent (or at least partial) functionality for non-Internet Explorer clients.

While Netscape 4 and earlier browsers also include a variety of proprietary features, their relevance is quickly fading. Netscape 6 and 7 marked a sharp departure from traditional browser trends. These browsers were based upon the Mozilla open source project that continues to live on and emphasize standards support over proprietary features. This departure has the lofty goal of creating standardized browser engines so that developers can write one script rather than numerous conditional scripts for each browser version and vendor. While this goal isn’t quite here yet, it draws closer every year. Until that time, we will have to apply the proprietary features specific to each browser carefully.