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Sub Procedures
A Sub procedure is a series of VBScript statements
(enclosed by Sub and End Sub statements) that
perform actions but don't return a value. A Sub
procedure can take arguments (constants, variables, or
expressions that are passed by a calling procedure). If a Sub
procedure has no arguments, its Sub statement must
include an empty set of parentheses ().
The following Sub procedure uses two intrinsic, or
built-in, VBScript functions, MsgBox
and InputBox, to prompt a
user for information. It then displays the results of a
calculation based on that information. The calculation is
performed in a Function procedure created using
VBScript. The Function procedure is shown after the
following discussion.
Sub ConvertTemp()
temp = InputBox("Please enter the temperature in degrees F.", 1)
MsgBox "The temperature is " & Celsius(temp) & " degrees C."
End Sub
Function Procedures
A Function procedure is a series of VBScript
statements enclosed by the Function and End
Function statements. A Function procedure is
similar to a Sub procedure, but can also return a
value. A Function procedure can take arguments
(constants, variables, or expressions that are passed to it
by a calling procedure). If a Function procedure has
no arguments, its Function statement must include an
empty set of parentheses. A Function returns a value
by assigning a value to its name in one or more statements
of the procedure. The return type of a Function is
always a Variant.
In the following example, the Celsius function calculates
degrees Celsius from degrees Fahrenheit. When the function
is called from the ConvertTemp Sub procedure, a
variable containing the argument value is passed to the
function. The result of the calculation is returned to the
calling procedure and displayed in a message box.
Sub ConvertTemp()
temp = InputBox("Please enter the temperature in degrees F.", 1)
MsgBox "The temperature is " & Celsius(temp) & " degrees C."
End Sub
Function Celsius(fDegrees)
Celsius = (fDegrees - 32) * 5 / 9
End Function
Getting Data into and out of Procedures
Each piece of data is passed into your procedures using
an argument . Arguments serve as placeholders for the data
you want to pass into your procedure. You can name your
arguments any valid variable name. When you create a
procedure using either the Sub statement or the Function
statement, parentheses must be included after the name of
the procedure. Any arguments are placed inside these
parentheses, separated by commas. For example, in the
following example, fDegrees is a placeholder
for the value being passed into the Celsius function for
conversion.
Function Celsius(fDegrees)
Celsius = (fDegrees - 32) * 5 / 9
End Function
To get data out of a procedure, you must use a Function.
Remember, a Function procedure can return a value; a Sub
procedure can't.
Using Sub and Function Procedures in Code
A Function in your code must always be used on the
right side of a variable assignment or in an expression. For
example:
Temp = Celsius(fDegrees)
-or-
MsgBox "The Celsius temperature is " & Celsius(fDegrees) & " degrees."
To call a Sub procedure from another procedure,
type the name of the procedure along with values for any
required arguments, each separated by a comma. The Call
statement is not required, but if you do use it, you must
enclose any arguments in parentheses.
The following example shows two calls to the MyProc
procedure. One uses the Call statement in the code;
the other doesn't. Both do exactly the same thing.
Call MyProc(firstarg, secondarg)
MyProc firstarg, secondarg
Notice that the parentheses are omitted in the call when
the Call statement isn't used.
Try Yourself
1. Open a text editor type following code.
<HTML>
<HEAD><TITLE>Hello World</TITLE>
<SCRIPT LANGUAGE="VBScript">
<!--
Sub Button1_OnClick
MsgBox "Hello to VBScript"
End Sub
-->
</SCRIPT>
</HEAD>
<BODY>
<H3>Welcome to VBScript</H3><HR>
<FORM><INPUT NAME="Button1"
TYPE="BUTTON" VALUE="Click
Here"></FORM>
</BODY>
</HTML>
2. Save the file "Hello.HTM", open the file in
browser.
3. Click the button it shows the message "Hello to
VBScript"
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