JavaScript is no longer strictly limited to Netscape's browsers. The leading competition in terms of features, including JavaScript, is Internet Explorer 3.0 from Microsoft, which was released in the summer of 1996.
Internet Explorer 3 offers many of the features found in Navigator 3, including JavaScript, Java applet support, and frames. On top of this, Internet Explorer includes some features not found in Navigator 3, including ActiveX support and support for additional scripting languages.
Given the strength of Microsoft's marketing capabilities, Internet Explorer is likely to gain a foothold next to Netscape in the browser market. For this reason, Web page authors who want to take advantage of interactive Web features such as frames and JavaScript need to be aware of Internet Explorer and its capabilities.
This chapter examines Internet Explorer and compares it with Navigator 3. It covers the following topics:
Even a quick glance at the feature set of Internet Explorer 3 reveals that one of Microsoft's main goals with this release was to play catch up and offer all of the features that currently make Navigator the most popular Web browser—both with users and with page designers who want to take advantage of the latest interactive technologies.
That wasn't enough for Microsoft, however. The company also has invested a lot of effort in trying to differentiate Internet Explorer 3 from its Netscape counterpart. These steps include ActiveX and VBScript to help draw current Microsoft application developer's into the Internet Explorer fold, and stating commitments to open standards. The following features are among those that differentiate Internet Explorer:
The first four are discussed in more detail later in this chapter. The issue of standards, however, deserves consideration.
An issue that is held to be vital by HTML and Web purists—one for which Netscape has received a lot of criticism—is adherence to the standards laid down by standards bodies on the Internet.
The argument goes something like this: All producers of browsers and Web servers should strictly adhere to the defined standards. This ensures the openness and inter-operability of the Web so that any document can easily be viewed on any browser.
However, leading software vendors such as Netscape have taken it upon themselves to push the standards envelope by defining and implementing features and extensions to HTML and, once they're adopted by the page developers and users, submitting them to the standards bodies for addition to the defined standards.
The problem this has generated is that leading-edge browsers often have incompatible tags and features, making it difficult to develop a single HTML file that takes advantage of new technology while being compatible with a wide-range of client browsers.
Although Netscape expresses support for open standards, it has been the focus of a lot of criticism on the Internet exactly because Netscape has taken it on themselves to push the standards envelope. In the past, Microsoft has done the same thing. With Internet Explorer 2, for instance, Microsoft introduced a handful of custom HTML tags that were neither part of the HTML definition or supported by Netscape.
With the release of Internet Explorer 3, however, Microsoft has changed its tune, voicing a commitment to standards as laid down by the World Wide Web Consortium (W3C).
As expressed by Microsoft, this commitment means they plan to implement all approved Internet standards, identify not-yet-approved tags in their documentation, and submit new extensions to the W3C before shipping them.
Of course, this doesn't guarantee that Internet Explorer will be fully compliant with a standard because the software can—and does—include yet-to-be-approved tags, any of which could end up not being included in the standard HTML definition.
Some of the most notable additions to Internet Explorer 3 are those new features that match those found in Navigator 3:
Microsoft takes a different approach to scripting than Netscape. They have implemented ActiveX scripting—a low-level scripting engine on top of which any ActiveX-enabled scripting language can be plugged-in. In this way Microsoft has implemented two scripting languages in Internet Explorer 3: VBScript (discussed later in this chapter) and JScript (a Java-Script-compatible scripting language).
This implementation of JavaScript is close to the one found in Navigator 3. Some of its unique differences are discussed in Chapter 22, "The Internet Explorer Object Model," when the Internet Explorer Object Model is examined.
Both Navigator 3 and Internet Explorer 3 now support embedded Java applets. Where Netscape integrates the support into Navigator, Microsoft distributed the support as a separate extension to beta versions of Internet Explorer, but the result is the same.
This Java support provides the requisite Java Virtual Machine for running Java applets in an interpreted mode and, like Navigator 3, adds a just-in-time Java compiler. Microsoft has taken a different approach than Netscape, allowing any JIT compiler to be used in Internet Explorer—not just the one provided by Microsoft. Navigator, on the other hand, only supports the Borland JIT Java compiler.
On top of this, Java can be used to build ActiveX controls. ActiveX controls are discussed later in this chapter.
It's hard to avoid frames these days. Numerous Web sites use them to enhance their interfaces and many browsers have made moves toward adding support for frames.
Microsoft has added full frame support to Internet Explorer 3 as well as experimenting with additional features such as in-line frames, borderless frames, and other features not found in Navigator 3, such as floating frames. Figure 21.1 shows an example of a floating frame.
Figure 21.1. Floating frames in Internet Explorer.
It's hard to ignore the role that plug-ins have come to play in the popularity and success of Navigator 2 and 3. Plug-ins have enabled users to add numerous features, including expanded file-format support, new interface elements, and complete applications to their Navigator browsers.
Given the popularity of plug-ins among software vendors, with a long list of companies offering plug-ins for everything from Microsoft Word viewing capabilities to world clocks, it is inevitable that Microsoft has included support for plug-ins.
Microsoft has implemented this support in such a way that plug-ins currently installed in Navigator will be detected and used by Internet Explorer when needed. In addition, new plug-ins can be installed either in Navigator or Internet Explorer and Internet Explorer will be able to use them.
Figure 21.2. Netscape plug-ins like this one from Corel can be used in Internet Explorer.
In addition to some of its own security features discussed later in this chapter, Microsoft has implemented the server and client authentication features found in Navigator 3. In addition, Secure Sockets Layer technology, Netscape's protocol for secure communication on the Internet used by many sites, is supported by Internet Explorer.
While it includes features common to Navigator 3, Internet Explorer 3 also includes several features not found in Netscape's browser:
Using the ActiveX scripting engine, Microsoft has added a second scripting language to Internet Explorer called VBScript. A subset of the widely-used Visual Basic programming language, VBScript is optimized for programming Web Pages and client-end interactivity in Internet Explorer.
VBScript is discussed in detail in Chapter 23, "Programming with VBScript."
Object-linking and embedding technology has been present in Windows and now Windows 95 for some time. Microsoft has repackaged and renamed the technology ActiveX for its application to network computing on the Internet and Intranets.
ActiveX controls is another name for OLE objects. ActiveX controls provide an alternative to Java applets for including small, embedded pieces of software in Web pages. These controls can be built in any language, including Visual C++ or Java, and can be built for a verity of purposes, such as supporting new file formats, extending the Internet Explorer interface, and more. Figures 21.3 and 21.4 are examples of ActiveX controls.
Figure 21.3. Microsoft's Marquee controls allows a scrolling marquee to be included in a Web page.
Figure 21.4. ActiveX controls can create special graphics effects such as this gradient.
The fact that ActiveX and OLE are essentially the same technology means that Internet Explorer can be made to take advantage of OLE-compliant applications and these applications can take advantage of pieces of Internet Explorer in order to gain Internet capabilities.
ActiveX controls are discussed in more detail in Chapter 24, "Using the ActiveX Control Pad."
HTML Layouts offer a degree of design and creative flexibility previously available only in CD-ROM based applications. Using the HTML Layout Control—an ActiveX control that extends Internet Explorer—it's possible to design a complex layout bringing together animated effects, interface elements, other ActiveX controls, and embedded objects, along with drag-and-drop capabilities—all in a fixed spatial relationship. This definition of a layout can then be included in an HTML page as an embedded object.
Producing HTML Layouts is discussed in more detail in Chapter 25, "JavaScript and the Future," where the ActiveX Control Pad is looked at in more detail.
Because of their commitment to implementing the entire body of approved HTML, which is currently HTML 3.2, as well as to introducing new features not yet approved by the standards bodies, there are several HTML features which have yet to be implemented (or fully implemented) in Navigator.
These include:
In addition to the support for the security features found in Navigator 3—which were described early in this chapter—Microsoft has added additional security features to Internet Explorer 3:
Microsoft offers more international localized versions of Internet Explorer than Netscape does for Navigator.
Microsoft has announced or made available Internet Explorer 3 in 25 localized versions, ranging from Simplified Chinese to Brazilian Portuguese to Norwegian. By comparison, Netscape can lay claim to only a little over 11 localized versions.
On top of this, Internet Explorer can accept language extension modules so that, for example, an English copy of the browser could access and display a Web page in Hungarian or Japanese or any other language.
Even with all its features, Internet Explorer still suffers from some limitations.
Foremost among these limitations is the lack of available platforms for Internet Explorer. Netscape Navigator 3 is currently available on 16 platforms including all versions of Windows, Macintosh, and a broad range of UNIX flavors including Linux, Solaris and HP-UX.
Internet Explorer 3, on the other hand, is only available for Windows 95 and Windows NT 4.0 at the time of writing this book. Microsoft was working on a Macintosh version, but it was only available in a beta version and there were no clear plans for UNIX ports of Internet Explorer.
This gives Netscape the upper hand in that, theoretically at least, one version of a Web site can be viewed on any platform using Navigator 3.
In addition to this, Internet Explorer does have some other limitations:
Given the easy availability of Internet Explorer and the dominance of Microsoft as the operating system vendor of choice in the home and small office markets, it seems likely that Microsoft will make strong in-roads against Netscape in the Web browser market.
While it is unlikely that Microsoft will be unable to completely usurp Netscape for the dominant market position, it seems likely that Internet Explorer is well-placed to break the complete hold that Netscape enjoys over the Web browser market.
This means that the future Web browser market is likely to be more evenly split, with Netscape and Microsoft sharing the two leading spots for some time to come.
This means that you will likely see increasing number of sites sporting "Designed for Internet Explorer" slogans the way you do now for Netscape Navigator. Some of the technology Microsoft has introduced in Internet Explorer 3.0 will likely find it's way into future releases of Netscape Navigator.
This chapter has shown you how Microsoft has taken a large step towards effectively competing with Netscape.
Given the strong feature-set and the likely increased use of Internet Explorer 3.0, it's important for developers who want to use interactivity tools such as JavaScript to understand the fundamentals of Internet Explorer 3.0.
The next few chapters cover several key features of Internet Explorer, including:
