VBScript Tutorials - Herong's Tutorial Examples

∟Error Handling Flag and the "Err" Object

This chapter provides tutorial examples and notes on runtime error handling. Topics include the default error handling behavior; 'On Error Resume Next' and 'On Error GoTo 0' statements; catching errors with (Err.Number > 0); clear Err object with Err.Clear(); raise your own errors with Err.Raise(...).

Error Handling Rules Overview

IE Option Setting - Enable Script Debugging

"On Error Resume Next" - Turning on Error Handling

"On Error GoTo 0" - Turning off Error Handling

"Err.Number" and "Err.Clear()" - Error Code and Clear Method

Built-in "Err" Object Properties and Methods

"Err.Raise()" - Raising Your Own Errors

Conclusions:

• Runtime errors will be managed by the host environment, if you don't manage them.
• "On Error Resume Next" turns on the error handling flag, which causes the host environment to continue executing the next statement after raising a runtime error.
• "On Error GoTo 0" turns off the error handling flag, which causes the host environment to stop executing the current procedure after raising a runtime error.
• The "Err" object is built-in object representing the last runtime error.
• "Err.Number > 0" can be used to see if a runtime error has occurred or not.
• "Err.Clear()" method can be used to clear the "Err" object.
• "Err.Raise()" method can be used to raise your own runtime errors.

Table of Contents

 About This Book

 Introduction of VBScript - Visual Basic Scripting Edition

 Variant Data Type, Subtypes, and Literals

 Arithmetic Operations

 Numeric Comparison Operations and Logical Operations

 String Operations - Concatenation and Comparison

 Variable Declaration and Assignment Statement

 Expression and Order of Operation Precedence

 Statement Syntax and Statement Types

 Array Data Type and Related Statements

 Array References and Array Assignment Statements

 Conditional Statements - "If ... Then" and "Select Case"

 Loop Statements - "For", "While", and "Do"

 "Function" and "Sub" Procedures

 Built-in Functions

 Inspecting Variables Received in Procedures

►Error Handling Flag and the "Err" Object

 Regular Expression Pattern Match and Replacement

 scrrun.dll - Scripting Runtime DLL Library

 Creating Your Own Classes

 IE Web Browser Supporting VBScript

 IIS ASP Server Supporting VBScript

 WSH (Windows Script Host)

 References

 Printable Copy - PDF Version