Vb Script Functions - Part 3

Control Flow Functions

Do...Loop Statement

Do...Loop: Repeats a block of statements while a condition is True or until a condition becomes True.

Syntax:

 Do [{While | Until} condition]
   [statements]
   [Exit Do]
   [statements]
Loop

OR

Do
   [statements]
   [Exit Do]
   [statements]
Loop [{While | Until} condition]

Arguments:

condition: Numeric or string expression that is True or False. If condition is Null, condition is treated as False.
statements: One or more statements that are repeated while or until condition is True.

Example:

'Do...Loop

Counter = 1

    Do While Counter < 4

                        Total =Inputbox("Please enter the total marks in numbers")
                       
                                    If   Total < 50 Then
                                   
                                                MsgBox  "Fail"
                                   
                                    ElseIf  Total >=50 and Total <=60   then
                                   
                                                Msgbox "Second Class"
                       
                                    ElseIf  Total >60 and Total <80   then
                                   
                                                Msgbox "First Class"
                       
                                    ElseIf  Total >=80  then
                                   
                                                Msgbox "Distinction"
                       
                                    Else
                       
                                                Msgbox "Invalid Marks"
                                   
                                    End If

        Counter = Counter + 1

        Loop


Example:

Counter = 1

            Do
                        Total =Inputbox("Please enter the total marks in numbers")
                       
                                    If   Total < 50 Then
                                   
                                                MsgBox  "Fail"
                                   
                                    ElseIf  Total >=50 and Total <=60   then
                                   
                                                Msgbox "Second Class"
                       
                                    ElseIf  Total >60 and Total <80   then
                                   
                                                Msgbox "First Class"
                       
                                    ElseIf  Total >=80  then
                                   
                                                Msgbox "Distinction"
                       
                                    Else
                       
                                                Msgbox "Invalid Marks"
                                   
                                    End If

        Counter = Counter + 1

        Loop until Counter > 4


Example:

   'Exit Do While loop

Do While Counter < 10

Counter=counter + 1

If  counter = 6 Then

    Exit Do

End If

Print Counter
    Loop


Example:

'Exit Do Until loop

Do
   
Counter=Counter + 1

If  Counter = 6 Then

    Exit Do

End If

Print Counter
   
   
Loop Until counter >11

For...Next Statement

For...Next: Repeats a group of statements a specified number of times.

Syntax:

For counter = start To end [Step step]
    [statements]
    [Exit For]
    [statements]
Next

Arguments:

counter: Numeric variable used as a loop counter. The variable can't be an array element or an element of a user-defined  type.
start: Initial value of counter.
end: Final value of counter.
step: Amount counter is changed each time through the loop. If not specified, step defaults to one.
statements: One or more statements between For and Next that are executed the specified number of times.

Example:

For...Next
   
    Counter = 1
   
    For  Counter = 1 to 4
   
    Total =Inputbox("Please enter the total marks in numbers")
                                                               If   Total < 50 Then
                                       
                                                    MsgBox  "Fail"
                                       
                                        ElseIf  Total >=50 and Total <=60   then
                                       
                                                    Msgbox "Second Class"
                           
                                        ElseIf  Total >60 and Total <80   then
                                       
                                                    Msgbox "First Class"
                           
                                        ElseIf  Total >=80  then
                                       
                                                    Msgbox "Distinction"
                           
                                        Else
                           
                                                    Msgbox "Invalid Marks"
                                       
                                        End If
    Next
   

Example:
' increment  loop by  3
   
    Counter = 1
    Result  = 0
    For  Counter = 1 to 10  step 3
   
    Result=Result + Counter
   
    Print Result
   
    Next
   
Example:
'Decrement loop by  2
   
    For  Counter = 10 to 1  step -2
   
    Print Counter
   
    Next

Example:
'Exit For Loop

For Counter=1 to 10

    If  Counter=6 Then
        Exit for
    End If
Print Counter
Next

For Each...Next Statement

For Each...Next: Repeats a group of statements for each element in an array or collection.

Syntax:

For Each element In group
   [statements]
   [Exit For]
   [statements]
Next [element]

Arguments:

element: Variable used to iterate through the elements of the collection or array. For collections, element can only be a Variant
Variable, a generic Object variable, or any specific Automation object variable. For arrays, element can only be a Variant variable.
group: Name of an object collection or array.
statements: One or more statements that are executed on each item in group.

If...Then...Else Statement

If...Then...Else: Conditionally executes a group of statements, depending on the value of an expression.

Syntax:

If condition Then statements [Else elsestatements ]

OR

If condition Then
   [statements]
[ElseIf condition-n Then
   [elseifstatements]] . . .
[Else
   [elsestatements]]
End If

Arguments:

condition: One or more of the following two types of expressions:
A numeric or string expression that evaluates to True or False. If condition is Null, condition is treated as False.
An expression of the form Type of objectname Is object type. The object name is any object reference and object typeis any valid object type. The expression is True if object name is of the object type specified by object type; otherwise it is False.
statements: One or more statements separated by colons; executed if condition is True.
condition-n:   Same as condition.
elseifstatements: One or more statements executed if the associated condition-n is True.
elsestatements: One or more statements executed if no previous condition or condition-n expression is True.

Example:
'If...Then...Else

Total = Inputbox("Please enter the total marks in number ")

            If   Total >= 50 Then
           
                        MsgBox  "Pass"
           
            Else
           
                        Msgbox "Fail"
           
            End If

Example:

'If....ElseIf

Total = Inputbox("Please enter the total marks in number")

            If   Total < 50 Then
           
                        MsgBox  "Fail"
           
            ElseIf  Total >=50 and Total <=60   then
           
                        Msgbox "Second Class"

            ElseIf  Total >60 and Total <80   then
           
                        Msgbox "First Class"

            ElseIf  Total >=80  then
           
                        Msgbox "Distinction"

            Else

                        Msgbox "Invalid Marks"
           
            End If

 Select Case statement

Select Case: Executes one of several groups of statements, depending on the value of an expression.

Syntax:

Select Case testexpression
   [Case expressionlist-n
      [statements-n]] . . .
   [Case Else expressionlist-n
      [elsestatements-n]]
End Select

Arguments:

testexpression: Any numeric or string expression.
expressionlist-n: Required if Case appears. Delimited list of one or more expressions.
statements-n: One or more statements executed if testexpression matches any part of expressionlist-n.
elsestatements-n: One or more statements executed if testexpression doesn't match any of the Case clauses.


Example:
'Select Case

Colour =Ucase( Inputbox("Please enter the colour of your choice"))

          Select Case Colour
       
                                    Case   "RED"
       
                                                            MsgBox  "Colour selected is Red"
       
                                    Case   "BLUE"
       
                                                            MsgBox  "Colour selected is Red"
       
                                    Case   "GREEN"
       
                                                            MsgBox  "Colour selected is Red"
       
                                    Case   ELSE
       
                                                            MsgBox  "Invalid Colour"
          End Select

While...Wend statement

While...Wend: Executes a series of statements as long as a given condition is True.

Syntax:

While condition
   Version [statements]
Wend

Arguments:

condition: Numeric or string expression that evaluates to True or False. If condition is Null, condition is treated as False.
statements: One or more statements executed while condition is True.

Example:
'While...Wend
    Counter =1
    While Counter < 4
    Total =Inputbox("Please enter the total marks in numbers")
                                                               If   Total < 50 Then
                                       
                                                    MsgBox  "Fail"
                                       
                                        ElseIf  Total >=50 and Total <=60   then
                                       
                                                    Msgbox "Second Class"
                           
                                        ElseIf  Total >60 and Total <80   then
                                       
                                                    Msgbox "First Class"
                           
                                        ElseIf  Total >=80  then
                                       
                                                    Msgbox "Distinction"
                           
                                        Else
                           
                                                    Msgbox "Invalid Marks"
                                       
                                        End If
   
     Counter=counter + 1
   
    Wend

With statement

With: Executes a series of statements on a single object.

Syntax:

With object
   statements
End With

Arguments:

object: Required. Name of an object or a function that returns an object.
statements: Required. One or more statements to be executed on object.