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VBScript is another scripting language that can be used on the WWW.
However, VBScript is based on Microsoft Visual Basic and only Internet Explorer
has a VBScript interpreter. Therefore, VBScript is not practical for many WWW purposes.
It can be used in intranets if everyone is restricted to using Internet Explorer to access the intranet.
It can also be used with Microsoft Servers to create ASP which use server-side
scripts that create content that is sent to the client's browser. In that case, the client's browser is not
restricted to Internet Explorer, as long as the content being sent is consistent for any WWW browser.
Putting the actual script code inside XHTML comments is considered good practice with VBScript as it is
with JavaScript, to prevent the code from being displayed in browsers that do not have VBScript interpreters.
This section will present a quick overview of client-side scripting with VBScript. Since the basics of
programming and scripting were covered in the section on JavaScript, only the basics of VBScript
will be covered and some of the differences between JavaScript and VBScript will be mentioned.
The reader should refer to the end of this document and
the reference section for more complete references on VBScript.
Unlike JavaScript, VBScript is a case-insensitive language. That means that it views uppercase and
lowercase letters to be the same. For example, it would see "num", "Num" and NUM" to be the same item
whereas JavaScript would view them as three separate entities.
JavaScript indicates the end of a statement with a semicolon, ;. However, in
VBScript, there is no character to indicate the end of a statement. The end of a line is
considered the end of a statement. If a statement is too long to fit on one line, the line continuation
character, _, the underscore character must be placed as the last character on the line to connect that line to the one immediately below.
In both languages, variables do not need to be declared before being used.
However, it is considered good programming practice to declare variables and to
include comments that indicate the purpose of the variables. In VBScript, the keyword
Dim is used to declare variables instead of the word var in JavaScript. In VBScript,
if the first line in a script or function is Option Explicit, then variables must be declared before use.
All variables in VBScript are of type variant. This data type can store different
data types such as strings, integers, floating point numbers, boolean, etc.
As in JavaScript, arrays in VBScript always start with the index value zero.
However, declaring an array in VBScript is done by giving the highest index value
needed rather than the size. The declaration
Dim a(5)
in VBScript declares an array of six elements numbered from zero to 5.
VBScript's arithmetic operators for addition, subtraction and multiplication are the
same as JavaScript's. However, VBScript uses two division operators: a / for
floating point division and a \ for integer division.
VBScript's comparison operators for less than, greater than, less than or equal to and
greater than or equal to are the same as JavaScript's. But the equal comparison operator
in VBScript is a single equal sign, =, and the not equal comparison operator is <>.
The logical operators in VBScript are:
And (logical AND)Or (logical OR)Not (logical NOT)Imp (logical implication)Xor (exclusive OR)Eqv (logical equivalence)
Since VBScript does not use end-of-statement characters and curly braces to
indicate "groups" of statements, the control structures in VBScript end with one
or more keywords such as End If, Wend (for While End), End Select, etc.
13.3.1 The If Statement
Here are two examples of VBScript's If statement:
(1)
If s = x Then
sum = sum + s
End If
(2)
If s = 0 Then
sum = 0
Else
sum = sum + s
End If
13.3.2 The Select Case Statement
The Select statement is VBScript's version of the JavaScript Switch
statement. The case statement in VBScript does not require the use of a break statement.
Any variant type can be used in the case comparisons. The default case is implemented
with a Case Else case statement. An example of a VBScript Select statement is:
Select Case choice
Case 1
Call MsgBox("You chose Door #1.")
Case 2
Call MsgBox("You chose Door #2.")
Case 3
Call MsgBox("You chose Door #3.")
Case Else
Call MsgBox("You chose to keep the $200.")
End Select
There are several means of performing iteration in VBScript. VBScript has two means of iteration that are similar to the while
loop in JavaScript: The While/Wend and the Do/While.
The VBScript For/Next structure has a significantly different structure than the JavaScript For loop.
Most importantly, the condition in the VBScript For/Next loop does not change
once the loop begins. As an example, consider the following:
x = 6
For y = 1 To x Step 1
x = x - 1
Next
The first line of the For/Next loop above initializes y to 1 and increments
y by 1 at each repetition of the loop. The condition "To x" means that the
loop will continue while y is less than or equal to x. The thing to be
careful about with the VBScript For/Next loop is that the condition
is fixed once the loop begins. That is, the condition is set at the beginning
of the loop, in this case from 1 to 6, and even though x is changing during the
execution of the loop, the condition of the loop does not change.
VBScript has two iteration structures that do not have duplicates in
JavaScript: The Do/Until Loop and the Do/Loop Until structures.
VBScript furnishes a number of functions for common math functions such as
Abs(), Sin(), Cos(), Log(), Sqr(), etc.
VBScript also furnishes a number of functions to determine the data type is
currently stored in a variable. These functions include IsArray(), IsDate(), IsEmpty(),
and IsNumeric().
VBScript provides a wider variety of string manipulation functions than does JavaScript.
Functions are available for searching a string, the length of a string, comparing strings,
trimming strings from the right or left, concatenating strings, replacing substrings, and more.
VBScript also furnishes a number of formatting functions for output.
These include functions for currency, dates and percents.
The VBScript equivalent of the JavaScript alert() box is the MsgBox().
To create a message box, you need to call the MsgBox() function.
The MsgBox() function takes 3 arguments or parameters. The first is a
string that will be displayed in the box. The second is optional and
allows the button on the box to be customized to another string.
The third is a string which will be the title on the box. For example, the call
Call MsgBox("The input was not a number", , "Error")
will create a dialog box with the first string displayed inside the box,
"Error" in the titlebar and an "OK" button for the user to dispatch the message box.
Note that even though the call above does not include the second,
optional parameter, a blank space separated from the other parameters by a comma is required.
The VBScript equivalent of the JavaScript prompt() box is the InputBox().
To create an input box, you need to call the InputBox() function.
The InputBox() function takes 5 arguments or parameters.
The first is a string that will be displayed in the box.
The second is a string that will appear on the title bar of the box.
The third is optional and provides an initial value for the input area.
The fourth and fifth parameters are x,y screen coordinates which determine where on
the screen the box will appear. The unit of the coordinates is twips.
(1440 twips is one inch). For example, the call
firstname = InputBox("Enter your first name", "Input", , 700, 700)
will place the input box approximately one half inch down and one half inch to
the right of the top left corner of the screen. Note that this function call does not include
the word "Call". Note also that this function returns the value entered by the user and
this value is assigned to the variable "firstname".
VBScript has two means of grouping statements that perform a function together.
One is to define a subroutine and the other is to define a function. The main difference is that
functions return a value and subroutines do not. Both functions and subroutines can take parameters.
Functions return values by assigning a value to the name of the function.
The XHTML file below contains a VBScript that defines a function called "WhichLarger" and a
subroutine called "GetNums_OnClick". Note that the function has assignment statements to
the name of the function. Note that when the function is called in the subroutine GetNums_OnClick,
the value returned by the function is assigned to a variable called "larger".
The subroutine "GetNums_OnClick" is called when the button called "GetNums" in the form is clicked.
Thus, the click event calls the subroutine.
<html>
<head>
<title>A Simple VBScript</title>
<script type="text/vbscript">
<!--
Option Explicit
Dim intTotal, num1, num2
Function WhichLarger(x, y)
If(x > y) Then
WhichLarger = x
Else
WhichLarger = y
End If
End Function
Sub GetNums_OnClick()
Dim larger, sum
num1 = InputBox("Enter an integer", "Input Box", , 700, 700)
num2 = InputBox("Enter an integer", "Input Box", , 3200, 3200)
larger = WhichLarger(num1, num2)
sum = CInt(num1) + CInt(num2)
Call MsgBox("The sum of the two numbers is " & sum & ". " &_
larger & " was the larger of the two numbers.")
End Sub
-->
</script>
</head>
<body>
Click the button to see what happens.
<form>
<input name="GetNums" type="button" value="Click Here" />
</form>
</body>
</html>
- Anderson-Freed, S. (2002) Weaving a Website: Programming in HTML, Javascript, Perl and Java. Prentice-Hall:NJ. ISBN 0-13-028220-0
- Dietel, H. M., Dietel, P. J. & Neito, T. R. (2001) Internet & World Wide Web: How to Program. 2nd Edition. Prentice Hall, NJ.
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