VBScript procedures

A procedures is a segment of code grouped into a single entity. The great thing about procedures is that you can re-use them. By doing so, you eliminate the need to re-type the same code over and over again. Once you implement a procedure, you can use its code by calling that procedure.

This tutorial focuses on:

Creating procedures
Using parameters
Calling procedures
Returning values
VBScript's built-in procedures

Creating procedures

There are two types of procedures in VBScript - Sub procedures and Function procedures.

Sub procedures

A Sub procedure can perform some actions, but CANNOT return values.

A Sub procedure is enclosed in Sub and End Sub.

Syntax:

Sub nameOfSubProcedure() actions to perform End Sub

Example:

Sub printText() document.write("Here is some text"); End Sub

Function procedures

A Function procedure can perform some actions, and can return values.

A Function procedure is enclosed in Function and End Function.

Syntax:

Function nameOfFunction() actions to perform End Function

Example:

Function printText() document.write("Here is some text"); End Function

Using parameters

Parameters are variables placed inside the parentheses of a sub procedure or a Function procedure which are used by the code inside the sub procedure or Function procedure in some way. Parameters are separated by commas.

Using parameters with a Sub procedure

Syntax:

Sub nameOfSubProcedure(param1, param2, etc.) actions to perform End Sub

Example:

Sub printName(name) document.write("Your name is " & name); End Sub

The above procedure takes a value supplied by its name parameter and prints a message on a webpage.

Using parameters with a Function procedure

Syntax:

Function nameOfSubProcedure(param1, param2, etc.) actions to perform End Function

Example:

Function printName(name) document.write("Your name is " & name); End Function

The above Function procedure takes a value supplied by its name parameter and prints a message on a webpage.

Calling procedures

Once you create a procedure, how do you actually use it? You have to call that procedure.

Calling a Sub procedure

To call a Sub procedure, refer to the name of the Sub procedure with the Call statement, and pass the appropriate parameter values to it (if there are any).

Syntax:

Call subProcedureToCall()

Example:

Sub printMessage() document.write("VBScript is a scripting language.") End Sub Call printMessage()

Output:

VBScript is a scripting language.

Calling a Function procedure

To call a Function procedure, refer to the name of the Function procedure with the Call statement, and pass the appropriate parameter values to it (if there are any).

Syntax:

Call FunctionProcedureToCall()

Example:

Function printMessage() document.write("VBScript is a scripting language.") End Function Call printMessage()

Output:

VBScript is a scripting language.

Returning values

Function procedures can be used to return values. By doing so, the Function procedure simply acts as a value after its code has been executed. This way, a variable can take the value of a Function procedure.

Syntax for returning a value from a Function procedure:

Function aFunction() aFunction = value End Function

Example:

Function greet() greet = "user" End Function document.write("Hello "&greet())

Output:

Hello user

VBScript's built-in procedures

VBScript has several built-in procedures you can use for various purposes.

abs() - will return the absolute value of a number
Len() - will return the length of a text string
IsNumeric - will return a boolean (true/false) value indicating whether a supplied value is a number or not
Date() - will return the current system date

VBScript's built-in procedures example:

Output:

5 5 False Today's date is: 1/1/2010