VBScript Reference Manual for InduSoft Web Studio

VBScript Reference Manual InduSoft Web Studio
On Error
Description Enables or disables error handling.
Usage On Error Resume Next
On Error GoTo 0
Arguments none
Remarks If you don't use an On Error Resume Next statement anywhere in your code, any run-time error
that occurs can cause an error message to be displayed and code execution stopped. However,
the host running the code determines the exact behavior. The host can sometimes opt to handle
such errors differently. In some cases, the script debugger may be invoked at the point of the
error. In still other cases, there may be no apparent indication that any error occurred because
the host does not to notify the user. Again, this is purely a function of how the host handles any
errors that occur.
Within any particular procedure, an error is not necessarily fatal as long as error-handling is
enabled somewhere along the call stack. If local error-handling is not enabled in a procedure and
an error occurs, control is passed back through the call stack until a procedure with error-handling
enabled is found and the error is handled at that point. If no procedure in the call stack is found to
have error-handling enabled, an error message is displayed at that point and execution stops or
the host handles the error as appropriate.
On Error Resume Next causes execution to continue with the statement immediately following
the statement that caused the run-time error, or with the statement immediately following the
most recent call out of the procedure containing the On Error Resume Next statement. This
allows execution to continue despite a run-time error. You can then build the error-handling
routine inline within the procedure.
An On Error Resume Next statement becomes inactive when another procedure is called, so
you should execute an On Error Resume Next statement in each called routine if you want inline
error handling within that routine. When a procedure is exited, the error-handling capability
reverts to whatever error-handling was in place before entering the exited procedure.
Use On Error GoTo 0 to disable error handling if you have previously enabled it using On Error
Resume Next.
See Also Err object, Exit
Example The following example illustrates use of the On Error Resume Next statement.
On Error Resume Next
Err.Raise 6 ' Raise an overflow error.
MsgBox "Error # " & CStr(Err.Number) & " " & Err.Description
Err.Clear ' Clear the error.
Option Explicit
Description Forces explicit declaration of all variables in a script.
Usage Option Explicit
Arguments none
Remarks If used, the Option Explicit statement must appear in a script before any other statements. A
compile-time error occurs whenever a variable is encountered that has not been previously
declared.
When you use the Option Explicit statement, you must explicitly declare all variables using the
Dim, Private, Public, or ReDim statements. If you attempt to use an undeclared variable name,
an error occurs.
Use Option Explicit to avoid incorrectly typing the name of an existing variable or to avoid
confusion in code where the scope of the variable is not clear.
Example The following example illustrates use of the Option Explicit statement.
Option Explicit ' Force explicit variable declaration.
Dim MyVar ' Declare variable.
184 InduSoft, Ltd.