Overview of VB Script

VBScript is a Microsoft scripting language.It is the default scripting language in ASP.
VBScript is a scripting language is a lightweight programming language.
It  is a light version of Microsoft’s programming language Visual Basic
It is only supported by Microsoft’s browsers (Internet Explorer)
It uses the Component Object Model to access elements of the environment

VB Scripting Syntax and Guidelines

VBScript is used to develop scripts to perform both simple and complex object-based tasks
The following general VBScript syntax rules and guidelines:

• Case-sensitivity – VBScript is not case sensitive by default .
  For example :
  The two statements are identical in VBScript.
  Browser(“Mercury”).Page(“Find a Flight:”).WebList(“toDay”).Select “31”
  browser(“mercury”).page(“find a flight:”).weblist(“today”).select “31”
• Text strings – When you enter a value as a text string, you must add quotation marks before and after the string.
• Variables – Used to store strings, integers, arrays and objects .
• Parentheses – To achieve the desired result and to avoid errors, we use parentheses () correctly in your statements.
• Comments – Comments are added wherever possible, to make your scripts easier to understand and maintain.
• Spaces – Spaces are ignored by VBScript and it improve clarity.

VB Script – Constants

A constant is a meaningful name that takes the place of a number or string and never changes. There are number of useful constants built-in Vbscript
The various categories of constants in VBScript.

• Color Constants
• Date and Time Constants
• Date Format Constants
• Miscellaneous Constants
• MsgBox Constants
• String Constants
• Tristate Constants
• VarType Constants

VB Script – Color Constants

Color Constants – Defines about the eight basic colors that can be used in scripting.
 

Constant	Value	Description
vbBlack	&h00	Black
vbRed	&hff	Red
vbGreen	&hff00	Green
vbYellow	&hffff	Yellow
vbBlue	hff0000	Blue
vbMagen	&hff00ff	Magen
vbCyan	&hffff00	Cyan
vbWhite	&hffffff	White

 

VB Script – Date and Time Constants

Date and Time : Defines about the date and time constants used by various date and time functions.
 

Constant	Value	Description
vbSunday	1	Sunday
vbMonday	2	Monday
vbTuesday	3	Tuesday
vbWednesday	4	Wednesday
vbThursday	5	Thursday
vbFriday	6	Friday
vbSaturday	7	Saturday

 

VB Script – Date Format Constants

 

Constant	Value	Explanation
vbGeneralDate	0	Display a date and/or time. Date and time display is determined by system settings.
vbLongDate	1	Display a date using the long date format as per computer settings.
vbShortDate	2	Display a date using the short date format as per computer’s regional settings.
vbLongTime	3	Display a time using the long time format as per computer settings.
vbShortTime	4	Display a time using the short time format as per computer’s regional settings.

VB Script – Errors

The Error that occur during the execution are classified into :

• VB Script runtime errors
• VB Script syntax errors

VB Script – Runtime Error

Runtime error – Unexpected errors that causes hindrance during  the execution of scripts

VB Script – Syntax errors

Syntax error – The error that results when the structure of one of your VBScript statements violates one or more of the grammatical rules of the VBScript scripting language.

 

VB Script – Functions

VB Script supports some well/pre defined functions for easy manipulations.Below pointers are some of the important functions.

VB Script – Keywords

Function	Value Return	Example
Empty	Used to indicate an uninitialized variable value. A variable value is uninitialized when it is first created and no value is assigned to it, or when a variable value is explicitly set to empty.	Dim Captain , Captain=“Dhoni”, Captain=Empty
Nothing	Used to indicate an uninitialized object value, or to disassociate an object variable from an object to release the system resources	Set ExcelOb=CreateObject(“Excel.Application”) , Set ExcelOb=Nothing.
Null	Used to indicate that  the variable has no data.	x = Null , x contains no valid data

VB Script – Methods

Function	Value Return	Example
Clear	Clears all the existing property values for the “err”.	Object.clear, On error resume next ; err.raise=6 ; err.clear ; msgbox err.number will return 0.
Replace Method	Replaces the text found in an regular expression search.	object.Replace(string1, string2) , Example : ReplaceTest = regEx.Replace(str1, replStr)
Execute	Executes a regular expression search against a string.	object.Execute(Str) -, Example : Var1 = 1,Var2 = 2;Execute(“Var1 = Var2 + 3”) Response.Write (Var1) will print 5.

VB Script – Operators

VBScript’s operators can be separated into four semi-distinct categories.
Math Operators

Operator	English	Example	Result
+	Addition	1+1	2
–	Subtraction	2-1	1
*	Multiplication	4*4	16
/	Division	4/2	2
^	Exponent	2^3	8
mod	Modulus	4 mod 3	1

Comparison Operators
 

Operator	English	Example	Result
=	Equal to	10=11	False
>	Greater than	10>9	True
<	Lesser than	9<8	False
>=	Greater than or equal to	4>=2	True
<=	Lesser than or equal to	2<=3	True
<>	Not equal to	4 <> 3	False

String Operators

Operator	English	Example	Result
&	Connected to	“Treno”&”vision”	Trenovision

Logical Operators

Operator	English	Example	Result
AND	Both must be true	True and True	True
OR	Either on must be true	True and False	True
NOT	Inverse of Truth	Not False	True

VB Script – Statements (Looping)

Looping statements are used to run the same block of code a specified number of times.

Function	Value Return	Example
For…Next statement	Use the For…Next statement to run a block of code a specified number of times	For i=0 to 2 msgbox “Wipro” End For ‘ will print Wipro three times.
For Each…Next Loop	A For Each…Next loop repeats a block of code for each item in a collection, or for each element of an array.	Cars=array(“Mercedez”,”Jaguar”) For each y in cars msgbox y Next ‘ Will print Mercedez and then Jaguar.
Do…Loop statement	The Do…Loop statement repeats a block of code while a condition is true, or until a condition becomes true.	Do While i>5 ‘some code Loop ‘ If i=4 , it will never get executed , if i=7 it will get executed until the ‘some code’ part return a value less than 5
While…Wend statement	Executes a series of statements as long as a given condition is True.	i=4 ,While i<5 msgbox “printed” i=6 Wend ‘ will print “printed” once in a message box.

VB Script – Conditional Statements

Conditional statements are used to perform different actions for different decisions.In VBScript we have four conditional statements:

Function	Value Return	Example
If statement	executes a set of code when a condition is true	Dim Cricketer , Cricketer=“Dhoni” If Cricketer=“Dhoni” Then msgbox “Top Ranking Player” End if.
If…Then…Else statement	Select one of two sets of lines to execute	Dim Mark , Mark=“50” If Mark>=“50” Then Msgbox “Pass” Else msgbox “fail” end if
If…Then…ElseIf statement	select one of many sets of lines to execute	Dim State , State=“Pass” If State=“Pass” Then msgbox “1” ElseIf  State=“Fail” Then msgbox “0” Else msgbox “The entered state is other than Pass or Fail” End If
Select Case statement	select one of many sets of lines to execute	Dim MonthInt, MonthInt=2 Select Case(MonthInt) Case “1” msgbox “January” Case “2” msgbox “February” Case else msgbox “Enter either 1 or 2” End Select

For Reference

http://www.irt.org/articles/js117/
http://www.tizag.com/vbscriptTutorial/
http://www.onestopqa.com/resources/VB%20Script%20Basics.pdf
http://www.quackit.com/vbscript/tutorial/