A variable is a named location in computer memory that you can use for storage of data during the execution of your scripts. You can use variables to:
- Store input from the user gathered via your web page
- Save data returned from functions
- Hold results from calculations
An Introduction to Variables
Let's look at a simple VBScript example to clarify the use of variables.
Sub testVariables_OnClick
Dim Name
Name = InputBox("Enter your name: ")
MsgBox "The name you entered is " & Name
End Sub
The first line of this example defines a sub procedure associated with the click event of a command button named testVariables.
On second line we declare a variable named Name. We are going to use this variable to store the name of the user when it is entered. The third line uses the InputBox function to first prompt for, and then return, the user's name. You will see more of the InputBox function later in this tutorial. The name it returns is stored in the Name variable.
The fourth line uses the MsgBox function to display the user's name. Finally, the sub procedure completes on line five.
Exactly how, and where, variables are stored is not important. What you use them for, and how you use them is important.
Declaring Variables
There are two methods for declaring variables in VBScript, explicitly and implicitly. You usually declare variables explicitly with the Dim statement:
Dim Name
This statement declares the variable Name. You can also declare multiple variables on one line as shown below, although it is preferable to declare each variable separately.
Variables can be declared implicitly by simply using the variable name within your script. This practice is not recommended. It leads to code that is prone to errors and more difficult to debug.
You can force VBScript to require all variables to be explicitly declared by including the statement Option Explicit at the start of every script. Any variable that is not explicitly declared will then generate an error.
Variable Naming Rules
- They must begin with an alphabetic character
- They cannot contain embedded periods
- They must be unique within the same scope. There is more on scopes later in this lesson
- They must be no longer than 255 characters
Variants and Subtypes
VBScript has a single data type called a variant. Variants have the ability to store different types of data. The types of data that a variant can store are referred to as subtypes. The table below describes the subtypes supported by VBScript.
Subtype | Description of Uses for Each Subtype |
Byte | Integer numbers between 0 to 255 |
Boolean | True and False |
Currency | Monetary values |
Date | Date and time |
Double | Extremely large numbers with decimal points |
Empty | The value that a variant holds before being used |
Error | An error number |
Integer | Large integers between -32,768 and 32,767 |
Long | Extremely large integers (-2,147,483,648 and 2,147,483,647) |
Object | Objects |
Null | No valid data |
Single | Large numbers with decimal points |
String | Character strings |
Assigning Values
You assign a value to a variable by using the following format:
Syntax:
Variable_name = value
Examples:
Name = "Rahul"
Age=50
Scope of Variables
The scope of a variable dictates where it can be used in your script. A variable's scope is determined by where it is declared. If it is declared within a procedure, it is referred to as a procedure-level variable and can only be used within that procedure. If it is declared outside of any procedure, it is a script-level variable and can be used throughout the script.
The example below demonstrates both script-level and procedure-level variables.
Dim counter
Sub cmdButton_onClick
Dim temp
End Sub
The variable counter is a script-level variable and can be utilized throughout the script. The variable temp exists only within the cmdButton_onClick sub-procedure.
