Iterative Constructs:

      Looping allows you to run a group of statements repeatedly.

      Some loops repeat statements until a condition is False;

      Others repeat statements until a condition are True.

      There are also loops that repeat statements a specific number of times.

      Following are the Iterative Statements available in VB Script.

      For … Next

      For Each … Next

      Do While/Until … Loop

      Do … Loop While/Until

      Do … Loop

      While … Wend

For … Next:

      Description:

      Repeats a group of statements a specified number of times.

      You can use For ... Next statements to run a block of statements a specific number of times.

      For loops, use a counter variable whose value increases or decreases with each repetition of the loop

      Syntax:

For i = 1 To N Step Inc

Statement1

                   Statement2

                   ……………..

                   ……………..

                   StatementN

Next

      I is the Variable for maintaining index for the loop.

      N is the number of times loop should iterate. Means loop statements should get iterates N number of times.

      Using the Step keyword, you can increase or decrease the counter variable Inc by the value you specify.

      Examples:

      For For i = 1 To 50

               MsgBox (i)             ‘ Displays 1 to 50 Numbars

Next

      For For i = 1 To 50 Step 2

               MsgBox (i)             ‘ Displays Even Numbers In Between 1 to 50

Next

      For For i = 2 To 50 Step 2

               MsgBox (i)             ‘ Displays Odd Numbers In Between 1 to 50

Next

For Each … Next:

      Description:

      A For Each...Next loop is similar to a For...Next loop.

      Instead of repeating the statements a specified number of times, a For Each...Next loop repeats a group of statements for each item in a collection of objects or for each element of an array.

      This is especially helpful if you don't know how many elements are in a collection.

      Syntax:

For Each I in Var

Statement1

                   Statement2

                   ……………..

                   ……………..

                   StatementN

Next

      Here Var is a variable of type collection of Objects/Elements/Values or Array

      Examples:

      For Each i In [1, 2, 3]

               MsgBox (i)             ‘ Displays 1, 2, 3

Next

      For Each i In arr(10)

               MsgBox (i)             ‘ Displays Array Elements in Arr

Next

Do While … Loop:

      Description:

      Repeats a block of statements while a Expression condition is True or until a condition becomes True.

      Syntax:

Do [While | Until Expression]  

  

          Statement1

                             Statement2

                             ……………..

                             ……………..

                             StatementN

          [Exit Do]    

Loop

      Examples:

      Do While iCount < 20               ‘Repeats until False    

             

              iCount = iCount + 1         ‘ Increment Counter.

              MsgBox(iCount)               ‘ Displays Numbers from 1 to 19

Loop

      Do Until iCount > 20                 ‘Repeats until True     

   

              iCount = iCount + 1         ‘ Increment Counter.

              MsgBox(iCount)               ‘ Displays Numbers from 1 to 20

Loop

Do … Loop While:

      Description:

      Repeats a block of statements while Expression condition is True or until a condition becomes True.

      Syntax:

Do

          Statement1

                             Statement2

                             ……………..

                             ……………..

                             StatementN

          [Exit Do]    

          Loop [While | Until Expression]   

      Examples:

      Do

              iCount = iCount + 1         ‘ Increment Counter.

              MsgBox(iCount)               ‘ Displays Numbers from 1 to 19

Loop While iCount < 20            ‘Repeats until False   

              

      Do

              iCount = iCount + 1         ‘ Increment Counter.

              MsgBox(iCount)               ‘ Displays Numbers from 1 to 20

      Loop Until iCount > 20             ‘Repeats until True       

 

While … Wend:

      Description:

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

      The While...Wend statement is provided in VBScript for those who are familiar with its usage.

      However, because of the lack of flexibility in While...Wend, it is recommended that you use Do...Loop instead.

      The While...Wend statement is provided in VBScript for those who are familiar with its usage.

      Syntax:

While Expression

          Statement1

                             Statement2

                             ……………..

                             ……………..

                             StatementN

[Exit Do]    

          WEnd

      Examples:

      While iCount < 20                     ‘Repeats until False

              iCount = iCount + 1         ‘ Increment Counter.

              MsgBox(iCount)               ‘ Displays Numbers from 1 to 19

Loop           

Exit Statement:

      Exits a block of Do...Loop, For...Next, Function, or Sub Statements.

      Exit Do

      Provides a way to exit a Do...Loop statement.

      It can be used only inside a Do...Loop statement.

      Exit For

      Provides a way to exit a For loop.

      It can be used only in a For...Next or For Each...Next loop.

      Exit Function

      Immediately exits the Function procedure in which it appears.

      Exit Property

      Immediately exits the Property procedure in which it appears.

      Exit Sub

      Immediately exits the Sub procedure in which it appears.