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All About Variables Part 3 : Checking for specific SubTypes
 [Part 1 | Part 2 | Part 3]

There are six different functions that will assist you in determining if a particular variable is one Subtype or another. Below I have listed all of the SubType checking functions:

IsArray(VariableToCheck)
IsDate(VariableToCheck)
IsEmpty(VariableToCheck)
IsNull(VariableToCheck)
IsNumeric(VariableToCheck)
IsObject(VariableToCheck)

All of the above functions return a boolean value (true or false). Some of the above are self explanatory, however a few are not as clear. I will go over the ones that need explaining:

IsEmpty(VariableToCheck)
     What makes a variable empty? If the variable has been created, but has not been assigned a value yet it is considered to be empty. This is different from a value that is empty ("") or equal to NULL.

IsNull(VariableToCheck)
     What makes a variable null? A variable is null only when it equals null. You can set a variable equal to null.

IsNumeric(VariableToCheck)
This will return true if the variable can be converted to a numeric SubType without generating an error.

Example:

 myVar = "Hello"
If IsNumeric(myVar) Then
     Response.Write("Variable is numeric.")
Else      Response.Write("Variable is NOT numeric.")
End If
Result:
Variable is NOT numeric.

Another way to determine the variable SubType is the VarType() function.

Syntax:
 VarType(VariableToCheck)

 The above function will return a number representing the various subtypes. I have listed them for you below:

Subtypes Value Description
vbEmpty 0 Not assigned a value
vbNull 1 No matching SubType
vbInteger 2 Integer
vbLong 3 Long
vbSingle 4 Single
vbDouble 5 Double
vbCurrency 6 Currency
vbDate 7 Date
vbString 8 String
vbObject 9 Object
vbError 10 Error
vbBoolean 11 Boolean (true or false)
vbVariant 12 Variant, array of variants only
vbDataObject 13 Data Access
vbDecimal 14 Decimal
vbByte 17 Byte
vbArray 8192 Array