VBScript variables
Variables are a fundamental concept in many computer languages and knowing how to work with them is essential knowledge.
This lesson focuses on:
- What is a variable?
- Declaring variables
- Option Explicit
- Naming variables
- Printing variables
What is a variable?
A variable is a container which stores information in a computer's memory. The value of a variable can change all throughout a script.
Declaring variables
In VBScript a variable is declared with the Dim statement.
Syntax:
Dim variableName
Example:
<script type="text/vbscript"> Dim title </script>
Once you declare a variable, you can give it a value.
Example of declaring a variable and then giving it a value:
<script type="text/vbscript"> Dim title title = "A book to read" </script>
In the above example a variable named title is declared. On the next line the variable title is assigned the value "A book to read"
NOTE: The Dim statement should be used only once with each variable - during declaration. After a variable has been declared, you can refer to it by its name without the Dim statement, as using the Dim statement to declare variables is optional, but doing so is good convention.
Option explicit
It is possible that within a script you will misspell a variable name and consequently get unexpected results. For example, if you misspell the variable name "title" as "titld", VBScript will automatically generate a variable with the name "titld". You can prevent this from happening by using the option explicit statement. This statement goes all the way at the top of a script, and when you use it, you must use the Dim statement to declare variables.
Example:
<script type="text/vbscript">
option explicit
Dim title
title = "A book to read"
</script>
Naming variables
When naming variables, several rules should be followed:
-
Make sure that the variable name is descriptive.
If you do not give a variable a descriptive name, it will be hard to understand what the variable refers to. For example, if you wanted to create a variable which would hold a value signifying the amount of chairs in a room, which variable name would be more appropriate - numChairs or a? The better choice for the variable name would be numChairs because it is more descriptive.
-
Make sure the variable name is of appropriate length.
Make sure the variable name is long enough to be descriptive, but not too long.
-
Do not use spaces in variable names.
This is a rule that must be followed in VBScript because VBScript does not allow spaces in variable names.
-
Do not use periods (.) in variable names
Variable names cannot contain periods.
-
Do not use special symbols in variable names such as !@#%^&*
As is the rules with spaces, special symbols are not allowed in variable names. Using special symbols in variable names will generate an error. There is however one special symbol that can be used in variable names, and that symbol is the underscore ( _ ) symbol. Variable names can only contain letters, numbers, or the underscore symbol.
-
Do not exceed 255 characters
Variable names cannot exceed 255 characters.
Printing variables
Variables are printed by including the variable name in a document.write() command. When printing the value of a variable, the variable name should NOT be included in double quotes.
Example:
<html>
<head>
<title>Printing variables</title>
</head>
<body>
<script type="text/vbscript">
Dim numChairs
numChairs = 5
document.write(numChairs)
</script>
</body>
</html>
Output:
You can also print variables together with regular text. To do this, use the & symbol to join the text and variable values together.
Example:
<html>
<head>
<title>Printing variables and text together</title>
</head>
<body>
<script type="text/vbscript">
Dim teamName, teamState, numWins, numLosses
teamName = "The Penguins"
teamState = "Connecticut"
numWins = 12
numLosses = 2
document.write("The name of the team is " & teamName)
document.write("<br />The team is from " & teamState)
document.write("<br />" & teamName & " have won "
& numWins & " games and have lost " & numLosses & " games")
</script>
</body>
</html>
Output:
The team is from Connecticut
The Penguins have won 12 games and have lost 2 games
