Empty - The Default Value of a Variable

VBScript Tutorials - Herong's Tutorial Examples

∟Variable Declaration and Assignment Statement

∟Empty - The Default Value of a Variable

This section provides a tutorial example on how to find out the default value, Empty, of a variable before its first assignment.

What is the default, or initial, value of a variable after the declaration and before the first assignment? The answer is: Empty.

There are 3 ways to check if a variable has the Empty value:

Using the IsEmpty(variable_name) function to return a Boolean value True.
Using the VarType(variable_name) function to return a predefined constant, vbEmpty.
Using the TypeName(variable_name) function to return a string, "Empty".

Here is a tutorial example on how to check the default value of a variable:

<html>
<body>
<!-- default_value.html
 - Copyright (c) 1998 HerongYang.com. All Rights Reserved.
-->
<pre>
<script language="vbscript">
   ' Variable, author, is explicitly declared
   Dim author
   document.writeln()
   document.writeln("author = " & author)
   document.writeln("IsEmpty(author) = " & IsEmpty(author))
   document.writeln("(VarType(author)=vbEmpty) = " _ 
      & (VarType(author)=vbEmpty))
   document.writeln("TypeName(author) = " & TypeName(author))

   ' Variable, buffer, is implicitly declared
   document.writeln()
   document.writeln("buffer = " & buffer)
   document.writeln("IsEmpty(buffer) = " & IsEmpty(buffer))
   document.writeln("(VarType(buffer)=vbEmpty) = " _ 
      & (VarType(buffer)=vbEmpty))
   document.writeln("TypeName(buffer) = " & TypeName(buffer))
</script>
</pre>
</body>
</html>

Here is the output of this VBScript example:

author = 
IsEmpty(author) = True
(VarType(author)=vbEmpty) = True
TypeName(author) = Empty

buffer = 
IsEmpty(buffer) = True
(VarType(buffer)=vbEmpty) = True
TypeName(buffer) = Empty