“Continue” (to next iteration) on VBScript

Question

A colleague and I were trying to figure out a way of doing the equivalent of a \"continue\" statement within a VBScript \"For/Next\" loop.

Everywhere we looked we found

Answer 1

One option would be to put all the code in the loop inside a Sub and then just return from that Sub when you want to "continue".

Not perfect, but I think it would be less confusing that the extra loop.

Answer 2

I think you are intended to contain ALL YOUR LOGIC under your if statement. Basically:

' PRINTS EVERYTHING EXCEPT 4
For i = 0 To 10
  ' you want to say
  ' If i = 4 CONTINUE but VBScript has no continue
  If i <> 4 Then ' just invert the logic
    WSH.Echo( i )
  End If
Next

This can make the code a bit longer, but some people don't like break or continue anyway.

Answer 3

Implement the iteration as a recursive function.

Function Iterate( i , N )
  If i == N Then
      Exit Function
  End If
  [Code]
  If Condition1 Then
     Call Iterate( i+1, N );
     Exit Function
  End If

  [Code]
  If Condition2 Then
     Call Iterate( i+1, N );
     Exit Function
  End If
  Call Iterate( i+1, N );
End Function

Start with a call to Iterate( 1, N )

Answer 4

A solution I decided on involved the use of a boolean variable to track if the for loop should process its instructions or skip to the next iteration:

Dim continue

For Each item In collection
    continue = True

    If condition1 Then continue = False End If

    If continue Then
        'Do work
    End If
Next

I found the nested loop solutions to be somewhat confusing readability wise. This method also has its own pitfalls since the loop doesn't immediately skip to the next iteration after encountering continue. It would be possible for a later condition to reverse the state of continue. It also has a secondary construct within the initial loop, and requires the declaration of an extra var.

Oh, VBScript...sigh.

Also, if you want to use the accepted answer, which isn't too bad readability wise, you could couple that with the use of : to merge the two loops into what appears to be one:

Dim i

For i = 0 To 10 : Do
    If i = 4 Then Exit Do
    WScript.Echo i
Loop While False : Next

I found it useful to eliminate the extra level of indentation.

Answer 5

Your suggestion would work, but using a Do loop might be a little more readable.

This is actually an idiom in C - instead of using a goto, you can have a do { } while (0) loop with a break statement if you want to bail out of the construct early.

Dim i

For i = 0 To 10
    Do
        If i = 4 Then Exit Do
        WScript.Echo i
    Loop While False
Next

As crush suggests, it looks a little better if you remove the extra indentation level.

Dim i

For i = 0 To 10: Do
    If i = 4 Then Exit Do
    WScript.Echo i
Loop While False: Next

Answer 6

Try use While/Wend and Do While / Loop statements...

i = 1
While i < N + 1
Do While true
    [Code]
    If Condition1 Then
       Exit Do
    End If

    [MoreCode]
    If Condition2 Then
       Exit Do
    End If

    [...]

    Exit Do
Loop
Wend