detect a 'Error: Object doesn't support this property or method'

Question

The object I'm working on is instantiated in javascript, but used in VBSctipt. In one code path the variable M.DOM.IPt is defined and has a value, however, in the other it is not. I need to detect if it has been defined or not. I checked that M.DOM is defined and accessable in both code paths. Every test I have tried simply results in Error: Object doesn't support this property or method.

I have tried:

• IsEmpty(M.DOM.IPt)
• M.DOM.IPt is Nothing
• isNull(M.DOM.IPt)

Is there any way to detect the variable isn't defined and avoid the error?

note: I can put On Error Resume Next in and it will simply ignore the error, but I actually need to detect it and conditionally do something about it.

Answer 1

Have you tried On Error Goto label?

Answer 2

On Error Resume Next
Err.Clear
MyVariable=M.DOM.Ipt
If Err.Number<> 0 Then
    'error occured - Ipt not defined
    'do your processing here
Else
    'no error - Ipt is defined
    'do your processing here
End If

Answer 3

    Function SupportsMember(object, memberName)
      On Error Resume Next

      Dim x
      Eval("x = object."+memberName)

      If Err = 438 Then 
        SupportsMember = False
      Else 
        SupportsMember = True
      End If

      On Error Goto 0 'clears error
    End Function