- Special Edition Using Visual Basic Script -

CHAPTER 13 - Comparing VBScript, VBA, and Visual Basic

by Ron Schwarz

This chapter addresses the differences you'll encounter when coming to VBScript from a background in one of the "traditional" VB dialects (VB/VBA).

• VBScript For VB Programmers
• Find out the VB features that are not supported, or behave differently in VBScript.
• Syntax Differences
• Learn how to deal with Declaration and Language constraints.
• Design Interface Issues
• The ActiveX Control Pad is an excellent tool for developing VBScript Web page applications and content, but it's different from the VB IDE. Find out how this impacts your coding efforts.
• User Interface Issues
• VBScript does not create stand-alone applications. Well-designed script-enabled pages can help alleviate the differences. Find out how in this chapter.

Overview

Because VBS is a subset of VB, the bulk of the information provided in here consists of differencesùmainly differences of omissionùas documented by Microsoft at the time this book goes to press. (Some of this may change eventuallyùthe VBS specifications have changed more than once since work began on this book, but are expected stabilize shortly.)

Syntactical differences, covered in Table 13.1, Declaration Issues, and Table 13.2, Language Issues, are only part of the picture. If you're going to excel in what you're doing, you need to learn the nuances of the platform and accommodate yourself to it.

Trying to "force-fit" either existing code or existing skills to a new environment is tantamount to the backwoods axiom that advises, "Don't force it, use a bigger hammer!" Even if you do succeed in fitting the square peg to the round hole, neither you, nor your users are apt to be particularly satisfied with the results.

Therefore, it's an absolute necessity that you gear yourself to the language (VBScript) ,the development tools at hand (ActiveX Control Pad), and the presentation medium (Internet Explorer).

If you're a VB programmer, you can probably remember muddling through the documentation, the IDE, and the language, making small headway until things suddenly "clicked," and it started making sense. This event marked the beginning of your ability to "think in VB," and you can expect a similar illumination after playing with VBS and the Control Pad for a while.

Naturally, you will be able to leverage a considerable measure of your existing skills and language. But, it will quickly become apparent that VBS has its own gestalt. It's not too different from situations that occur with spoken language: Cantonese and Mandarin are both "Chinese," but fluency in one does not equate to fluency in the other. So it is with VBS and the other dialects of VB.

You'll find some of the differences maddening at first, but the frustration will diminish as you begin to work instinctively.

There are two main reasons for omitted functionality. The first consideration is security (it would be poor form to make it easy for unscrupulous individuals to harm users who stumble upon their websites), and "weight" (because of issues such as download time and memory footprint, VBS is designed to be a "lightweight" implementation of the language).

Declaration Comparison

Table 13.1 covers the declaration changes documented by Microsoft. If you're experienced with one of the other dialects of VB (VB or VBA) you should take the time to familiarize yourself with the differences now, to avoid frustration later on.

Table 13.1 Declaration Issues

While not all VB funtionality is supported in VBScript, implemented features are fortunately highly compatible with their VB counterparts. This behavior carries over to most language elements, covered in the next section, "Language Comparison."

Language Comparison

Table 13.2 lists the changes in language elements at the time this book goes to press. There are significant differences between VB/VBA and VBScript. The changes are essentially changes of ommissionùwhile you will need to learn what to avoid, you won't have to relearn any implemented features, since syntax remains consistent.

Table 13.2 Language Issues

As you can see from Table 13.2, there are quite a few VB features that are unimplemented in VBScript. The reasons are threefold: VBScript is designed to be a lightweight language for performance and resource reasons, it's necessary to prevent potential for damage via "dangerous" functions, and, the Web page platform has different characteristics than a VB program. The next section, "Style Differences," shows you how to accommodate yourself to the differences covered so far in this chapter.

Style Differences

Just as VB programming requires a change in philosophy from non-GUI programming, creating script-enabled Web pages hosted in a WWW browser mandates a new way of thinking and coding. To further complicate matters, the Internet is undergoing a series of concurrentùand majorùtransformations. If change indeed brings opportunity, the Internet is likewise what might be termed a "target-rich environment." It has lots of potential, and it has lots of risk. Surfing the Web is more accurate an aphorism than it might seem; the trick is to stay on top of the wave.

If you come from a traditional HTML programming background, your head is probably spinning about now. It'll pass. The Web will remain content-heavy, but the fantastic array of ActiveX controls, combined with HTML Layout Page functionality will provide the ability to do more than ever before, and to do it easier than you ever imagined. You'll have to learn to think in new ways, and at first, you'll need to resist the temptation to do things the old way. As long as the traditional HTML methods are more familiar to you than the new ActiveX features, you'll have to discipline yourself to work with the new capabilities, but it will be worth it in the long run, and besides, it won't take that long.

VB programmers, on the other hand, will probably feel like they're back in the training-wheel stage. To an extent, it's an accurate perception: VBS is rather limited when compared to VB 4.0. But, unlike traditional VB programming, where the program is the totality of your efforts, or even VBA development, where you have freedom from language and security restrictions, VBScript applications are documents, and the code itself takes a role subservient to the end product.The changes of style affect you, as a developer, and, they affect the people who use what you write. Whether you're creating Internet pages, used by anyone who stumbles onto your site, or vertical-market intranet systems, you'll have to conform yourself to the realities and requirements of the medium, and the needs and expectations of the users.The following sections focus on the issues you'll need to keep in mind when working with VBScript.

Development Environment

The ActiveX Control Pad (covered in detail in Chapters 3-5) provides an excellent platform for creating script-enabled Web pages. However, convenient and powerful as it may be, it is not a full-featured IDE. In addition to the features that are available in VB, but are not present in the Control Pad, you'll have to deal with the "look and feel" differences, and limitations imposed by the target platform.

Error Control

The area that is perhaps most notable in its absence is any type of debugging facility. Because scripts are only one part of a page, it may be some time before there's much debugging capability built-in to VBS development tools. (When you reflect on the complexity of the Internet Explorer, and consider that any debugger worth its salt would have to emulate the IE, in addition to being able to interpret VBScript with the level of detail offered by VBùbreakpoints, single-step, expression watches, etc.ùit becomes apparent that the undertaking would bemonumental.)

This being acknowledged, you do still have to deal with debugging issues, and the onus is entirely on you at this stage of the game. What to do? First and foremost, read Appendix C, "VBScript Coding Conventions," and take its message to heart. By rigorously adhering to a set of standards, your code will be readable and understandable, and as a result, you'llbe better prepared to comprehend it later on.

Use Option Explicit to help prevent errors caused by typos. Yes, even with Option Explicit turned on, you won't find undeclared variables until you're running your page in the Internet Explorer, but at least you will find them.

Layout Management

When you're first learning VBScript, you'll probably experiment with Notepad, or an equivalent ASCII text editor. It's a fast, easy way to enter a few lines of code and save them to a file. However, once you begin to gain an understanding of ActiveX "stuff" (of which VBScript is but one part), you'll need to make the transition to the ActiveX Control Pad.

While it's true that anything the Control Pad can do interactively, you can do manually in Notepad, it's also true that you can walk from New York to California. This is especially important to remember if you're really good in HTML, because you will have to consciously depart from familiar territory to something completely new and alien.

It's likely that HTML as we know it is dead. It may not know it's dead, and maybe a lot of HTML-oriented folks don't know it's dead either. But, that doesn't change the reality that the new Layout Page flexibility has been needed for some time, and is finally available. HTML will remain as the underlying container, but the old-style flow-of-text formatting is gone, gone, gone, once ActiveX takes hold.

Why is this such a big deal?

Consider for a moment the confusion that surrounds HTML. The proliferation of new, proprietary formatting codesùeverything from special font handling commands to table codes (and everything in between) exists to provide a measure of control over the appearance of the final product. The fact that it's possible at all, given the underlying formatting model, is a testament to the ability of the people writing browser software.

But, it's resulted in language-bloat of gargantuan proportion. It's hard to believe that anyone is proficient in the near-countless codes, let alone the variations between one browser and another.

The "big deal" is this: HTML Layout Pages provide a simple, elegant, and workable solution to the problems of placing, sizing, and formatting content and active elements in a web page. They sweep away the need for the vast majority of HTML arcana, and render much of it functionally obsolete. If it was a movie, it would be called, "Buggy-whip manufacturers vs. the Model T Redux."

The moral is, don't be so attached to the old way of doing things that you miss out on the opportunity that the new technology presents. It can become a personal issue, especially if you are proficient in the existing system, but don't make the same mistake that so many have before during times of change. Remember the countless programmers who stayed with CP/M, because they thought, "MSDOS will never make it," or, the ones who stayed too long at the C: prompt, because "Windows? Who needs it!".

It's good to learn from your mistakes. It's better to learn from the mistakes of others. Remember: the trick is to stay on top of the wave.

User Environment

When desktop publishing software first became widely available, there was a wave of what were snickeringly referred to as "Ransom Notes"ùdocuments with numerous typefaces and sizes all on one sheet. People went wild playing with fonts, pitches, attributes, and formatting. Everyone became an instant typesetter. People who should have been managing operations instead spent their time playing at "publishing," and simple memos turned into major productions, replete with grammatical and spelling errors galore.

Marshall McCluhan said, "The medium is the message." The sad fact is, people naturally tend to get wrapped up in the glitz and trappings of something new, especially when that something is a graphical presentation system.

While this book can't cover everything you'll ever need to know about style, layout, and presentation, it can at least give you some pointers, and aim you in the right direction.

The first bit of advice is simple. Simple, as in "Keep It Simple." Resist the temptation to do everything, everywhere, every time. You don't really have to use every last feature offered by ActiveX and VBS in each project you create. To be sure, the temptation will be thereùwhen it's easy to drop a group of controls into a tabbed container, and surround it with buttons and pictures and... You get the idea. Present the users with what needs to be presented, in a visually attractive manner, without overwhelming them. Sensory overload is not a pretty sight.

One of the best sources of design insight is available to you immediately. Take a look at the different types of web pages that are posted on thenet. As of late, Microsoft seems to be paying particular attention to design issues, and, they seem to be doing a good job of it. Their pages are logical, relatively fast loading, and contain quite a bit of content without appearing "busy" or confusing.

Other sites go to the other extreme. You've probably landed at one time or another on a page that took fifteen minutes to load, and consisted of miles of links and random bitmaps all arranged in an incredibly long single column down one drawn-out page.

Some general, and near universal rules are easy to follow: avoid clutterùdon't cram large numbers of controls on one page. If it's really necessary to have a lot of controls, use a tabbed container, and place the controls on tabs according to logical considerations. Try to put yourself in the place of the users. Remember that having thought up, written, debugged, and tested your project, you are intimately familiar with it in its entirety, but, a user dealing with it for the first time will find it all new, and no matter how well-designed it is, a bit intimidating.

The fallacy in our field is the notion that as software becomes increasingly powerful, it becomes increasingly difficult to use. The best illustration of the falsehood of this statement is the new change that is taking over Web programming. It's changing from something of finite capability and incredible complexity, to something of limitless potential, and less and less effort.

From Here...

For all the similarities between VB and VBScript, it is truly a major new approach to programming. The following resources will prove very valuable.

• See Chapters 3-5 for information on using the ActiveX Control Pad.
• See Chapters 15-20 for details on the VBScript language implementation.
• See Appendix C, "VBScript Coding Conventions," for hints on making your code maintainable by imposing consistent structure.
• See Que's Special Edition, Using VB 4, and Visual Basic 4 Expert Solutions, for extensive information on the Visual Basic language.
• Refer to the Microsoft Visual Basic Scripting Edition Language Reference, for exhaustive syntax descriptions and requirements of all statements, functions, and methods.