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What is VBScript?

• Based on the Visual Basic family of languages
• Supports object oriented features
• Interpreted
• Loosely Typed

Syntax Rules

• VBScript is not case sensitive
• Each statement can only exist on one line
• Statements can be either simple statements or compound statements

Naming Rules

• Must begin with a letter or the underscore 
• Good: count, strInfo, _data
• Bad: 2day, 4get, *count violate this rule.
• Cannot contain special characters except the underscore
• Good: Names using alphabets, numbers and the underscore.
• Bad: Names using symbols and other special characters.
• Cannot match a reserved word
• Bad: for, if, Select
• Must be unique within a context
• Must be less than 256 characters

Naming Convention

objDescriptiveName
obj
  Three letter prefix for the data type
DescriptiveName

• A descriptive name for the variable
• First letter of each word in upper case

Literal Types

Numeric

• 1
• 3.14
• 3E7

Boolean

• True
• False

Characters

• “Hello World”
• “123 Straw Lane”
• “43210”
• Date

#07/21/2006#

Variables

Dim variableName

• Variables hold values that can change during program execution
• They function just like temporary storage locations

Constants:

Const constantName = value

• Constant names hold values that cannot change during program execution

• Constants should be used in place of hard-coded values

Operations

• Operations are the many forms of computations, comparisons etc that can be performed in VB
• Most operations are binary in the form:
• operand1 operator operand2
• Other operations are unary in the form
• operator operand1
• When an operator has 2 symbols, you cannot separate them with a space:
• Good: 2 <> 3
• Bad: 2 <  > 3

Arithmetic

• Used to perform calculations
• Both operands must be numeric values
• The result is a numeric value

+    Addition
-    Subtraction, Negation
*    Multiplication
/    Division
^    Exponent
Mod    Modulo

Comparison:

• Used to compare the value of two items
• Both operands must be of the same data type

• The result is a Boolean value

=	Equality
<>	Inequality
<	Less than
>	Greater than
<=	Less than or equals
>=	Greater than or equals

Logical

And Truth Table:

• Conjunction
• Used when both conditions are required

Operand1	Operand2	Result
T	T	T
T	F	F
F	T	F
F	F	F

Or Truth Table

• Disjunction
• Used when either condition is sufficient

Operand1	Operand2	Result
T	T	T
T	F	T
F	T	T
F	F	F

Not Truth Table

• Unary Operand
• Used to change the value of a condition

Operand 1	Result
T	F
F	T

Assignment

• Changes the value of a variable
• =
• Uses the same symbol as an equality check operator.
• Assignment only occurs when used in any of the following forms:
• variable = literal value
• variable = expression
• variable = variable

Concatenation:

• Combines 2 data types for display as a string
• &

Branching

• Allows you to avoid running certain sections of your code
• Code is only executed when a condition (or conditions) evaluate to True
• Provides a single application the ability to react differently to different input values

If
If condition Then
    statement(s)
End If

• Performs an operation only if the condition evaluates to True

• Used when an action is either performed or not performed.

If…Else

If condition Then
    statement(s)
Else
    statement(s)
End If

• Performs the If portion only if the condition evaluates to True and the Else portion otherwise.
• Used in an either or scenario when an operation is always performed.

If…ElseIf

If condition1 Then
    statement(s)
ElseIf condition2 Then
    statement(s)
Else
    statement(s)
End If

• Only one section can be executed even if many conditions evaluate to True.
• Used in a multiple choice scenario
• Inclusion of the last Else is optional

Loops

• Allows you to repeat running certain sections of your code
• Code executes when a condition (or conditions) evaluate to True
• Be careful with Loops. They can result in infinite processing.
• Forms
• Entry Condition
• Entry only when a initial condition is met
• Iterated
• Repeats for a specific number of times

Loop Questions:

While
 While condition
    statement(s)
Wend

• Entry Condition Loop
• Simplest form of the loop
• Requires manual modification of the loop condition

For
For variable = start To finish [Step change]
    statement(s)
Next

• Iterated Loop
• Favored because all the loop details are in the definition statement

Examples:

Declaring Variables:

dim name
name=some value

Assigning Values to Variables

name="Hege"
i=200 

If....Then.....Else

if i=10 Then
   msgbox "Hello"
   i = i+1
end If

if i=10 then
   msgbox "Hello"
else
   msgbox "Goodbye"
end If 

if payment="Cash" then
   msgbox "You are going to pay cash!"
 elseif payment="Visa" then
   msgbox "You are going to pay with visa."
 elseif payment="AmEx" then
   msgbox "You are going to pay with American Express."
 else
   msgbox "Unknown method of payment."
end If    

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