Example - Passing Arguments by Reference

VBScript Tutorials - Herong's Tutorial Examples

∟Example - Passing Arguments by Reference

This section provides a tutorial example on how to pass arguments by reference to swap values passed through procedure arguments.

To see how passing arguments by reference works, I wrote the following example, function_swap_by_ref.html:

<html>
<body>
<!-- function_swap_by_ref.html
 - Copyright (c) 1998 HerongYang.com. All Rights Reserved.
-->
<pre>
<script language="vbscript">
   document.writeln("")
   document.writeln("Test 1: Swapping two literals by reference")
   document.writeln("   Before Sub: " & "Apple" & " | " & "Orange")
   Call SwapByRef("Apple", "Orange")
   document.writeln("   After Sub: " & "Apple" & " | " & "Orange")

   vFirst = "Dog"
   vSecond = "Cat"
   document.writeln("")
   document.writeln("Test 2: Swapping two variables by reference")
   document.writeln("   Before Sub: " & vFirst & " | " & vSecond)
   Call SwapByRef(vFirst, vSecond)
   document.writeln("   After Sub: " & vFirst & " | " & vSecond)

Sub SwapByRef(ByRef vLeft, ByRef vRight)
   vTemp = vLeft
   vLeft = vRight
   vRight = vTemp
   document.writeln("   In Sub: " & vLeft & " | " & vRight)
End Sub
</script>
</pre>
</body>
</html>

Here is the output:


Test 1: Swapping two literals by reference
   Before Sub: Apple | Orange
   In Sub: Orange | Apple
   After Sub: Apple | Orange

Test 2: Swapping two variables by reference
   Before Sub: Dog | Cat
   In Sub: Cat | Dog
   After Sub: Cat | Dog

Here are my notes about this example:

Test 1 shows that data literal can be used for a "ByRef" argument. By you will not be able to receive the change done by the subroutine.
Test 2 shows that using variable for a "ByRef" argument let us receive the change done by the subroutine. After the subroutine call, values in vFirst and vSecond have been swapped.
"ByRef" keyword is optional.