VBScript Keywords

Keywords	Description
Empty	Used to indicate an uninitialized variable value. When a variable is first created or its value is explicitly set to Empty, the variable value is uninitialized and the variable has not been assigned a value. Example: Dim x 'variable x is uninitialized! x="ff" 'variable x is no longer uninitialized x=Empty 'variable x is uninitialized! Note:This is not the same as Null!!
IsEmpty	Used to test whether a variable is uninitialized. Example: If (IsEmpty(x)) 'Is variable x uninitialized?
Nothing	Used to indicate an uninitialized object value, or to detach an object variable from the object to release system resources. Example: Set myObject=Nothing
Is Nothing	Used to test whether a value is an initialized object. Example: If (myObject Is Nothing) 'Is it unset? Note:If you compare a value with Nothing, you will not get the correct result! Example: If (myObject = Nothing) 'Always false!
Null	Used to indicate that a variable does not contain valid data. Null sets the value to "invalid", while Empty indicates that the value is "unset". Note:This is different from Empty or Nothing!! Example: x=Null 'x does not contain valid data
IsNull	Used to test whether a value contains invalid data. Example: if (IsNull(x)) 'Is x invalid?
True	Used to indicate that a Boolean condition is true (True is -1)
False	Used to indicate that a Boolean condition is false (False is 0)

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