B VBScript05

VBScript Session 5

What we learn last session? Branching Branching using If …Then…Else statement. Branching using Select Case

Subjects for session 5

Looping through code. Do…Loop While…Wend For…Next For…Each

Exit statement.

Looping Through Code

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

Do While/Until

Looping Through Code Using Do…Loop Statement Repeats a block of statements while a condition is True or until a condition becomes True. The following looping statements are available in VBScript: VBScrip t: Do [{While | Until} condition] [statements ] [Exit Do] [statements ] Loop

Do

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

condition]

Looping Through Code Using Do…Loop Statement You can exit a Do...Loop by using the Exit Do statement. Because you usually want to exit only in certain situations, such as to avoid an endless loop, you should use the Exit Do statement in the True statement block of an If ...Then ...Then... ...Else Else statement. If the condition is False, the loop runs as usual.

Looping Through Code Using Do…Loop Statement Dim bCheck, Count

bCheck = True : iCount = 0

' Initializ I nitialize e variables.

Do

' Outer loop.

Do While iCount < 20

iCount = iCount + 1

' Inner loop. loop. ' Increment Counter.

If iCount = 10 Then

' If condition is True...

bCheck = False

' set value of flag to False.

Exit Do

' Exit inner loop.

End If  Loop Loop Until bCheck = False

' Exit outer loop immediately.

Looping Through Code Using While…Wend Statement Executes a series of statements as long as a given condition is True. The While While... ...Wend Wend statement is provided in VBScript for those who are familiar with its usage. However, because of the lack of flexibility in While While... ...Wend Wend, it is recommended that you use Do Do... ...Loop Loop instead. The While While... ...Wend Wend statement is provided in VBScript for those who are familiar with its usage.

Looping Through Code Using For…Next Statement Repeats a group of statements a specified number of times. You can use For For... ...Next 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

Dim x For x = 1 To 50 MyProc Next

Looping Through Code Using For…Next Statement Using the Step keyword, you can increase or decrease the counter variable by the value you specify. In the following example, the counter variable j is incremented by 2 each time the loop repeats. When the loop is finished, the total is the sum of 2, 4, 6, 8, and 10.

Dim j, itotal For j = 2To 10Step 2 itotal = itotal + j Next Msg = "The total is " & itotal

Looping Through Code Using For…Next Statement You can exit any For...Next statement before the counter reaches its end value by using the Exit For statement. Because you usually want to exit only in certain situations, such as when an error occurs, you should use the Exit For statement in the True statement block of an If...Then...Else statement. If the condition is False, the loop runs as usual.

Looping Through Code Using For Each...Next Statement 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.

Looping Through Code Exit Statement Exits a block of  Do...Loop, For...Next, Function, or Sub code. 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.

Excercises

Lab 5.1 Input parameters names are From and To Assume that both inputs are integers. Display in reporter all the pairs between For and To Use the For...Next loop. Tip Use the Step statement. Concatenate to a temporary string.

Try your program for the following values From = 2 : To T o = 10 (2,4,6,8,10) From = 1 : To = 9 (2,4,6,8) From = -7 : To T o = 3 (-6,-4,-2,0,2) From = 50 : To = 41 (50,48,46,44,42) From = -3 : To = -9 (-4,-6,-8)

Lab 5.2 Input parameters names are Pswd. Declare a constant MY_PASSWORD. Declare a constant MAX_RETRY = 3. If the password is correct display a micPass message. If the password is typed wrong more then MAX_RETRY times, display a micFail message. Use the Do..Loop (While or Until). Tip

Use the Exit Loop statement.

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