Variable Scope in Procedures
This section describes rules on scope of global variables defined in the main code and local variables defined in procedures.
Variable Scope - The area of source code where a variable is accessible.
If you are not using procedures, variable scope is very simple. The scope of a variable is: from the statement
where it is defined to the last statement of the code.
If you are using procedures, variable scope gets more complex. Here are some basic rules:
1. Global - If a variable is defined in the main code, its scope is from the statement where it is defined
to the last statement of the entire code including all procedures.
2. Local - If a variable is defined in a procedure code, its scope is from the statement where it is defined
to the last statement of the procedure.
3. Collision - If a variable is explicitly defined in a procedure code has the same name as a variable defined
in the main code, the variable of the main code become in-accessible within this procedure.
There are some interesting consequences of those rules:
- The nice thing about rule #1 is that variables defined the main code are automatically accessible in all procedures.
You don't have to pass them as reference arguments to share them in a procedure.
- The bad thing about rule #2 is that if you are using temporary variable in a procedure without explicit
declaration, you could accidentally change the value of a global variable of the same name.
- Rule #3 helps us to avoid the bad impact of rule #3, if you declare all temporary variables explicitly in procedures.
Table of Contents
About This Book
Introduction of VBScript - Visual Basic Scripting Edition
Variant Data Type, Subtypes, and Literals
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
What Is a Procedure?
"Function" Statement and Function Call
Function Procedure Example
"Sub" Statement and Subroutine Call
Sub (Subroutine) Procedure Example
Passing Arguments to Procedures
Example - Passing Arguments by Reference
Example - Passing Arguments by Value
Passing Arrays as Arguments
►Variable Scope in Procedures
Example - Variable Scope in Procedures
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)
Full Version in PDF/EPUB