VBScript Functions

last modified February 19, 2025

In this article, we will learn how to create and use functions in VBScript. Functions are reusable blocks of code that perform specific tasks. They help organize code and make it easier to maintain. We will use WScript.Echo to output results and run the scripts using cscript.

Simple Function

The first example demonstrates how to create a simple function.

simple_function.vbs

Function Greet(name)
    Greet = "Hello, " & name & "!"
End Function

WScript.Echo Greet("John")

This example defines a function Greet that takes a parameter name and returns a greeting message.

Function with Multiple Parameters

Functions can accept multiple parameters.

multi_param_function.vbs

Function Add(a, b)
    Add = a + b
End Function

WScript.Echo "Sum: " & Add(5, 3)

This example defines a function Add that takes two parameters and returns their sum.

Function with Optional Parameters

VBScript does not support true optional parameters. The following are workarounds to achieve similar functionality.

optional_param_function.vbs

Function Multiply(a, b)
    If IsEmpty(b) Then
        Multiply = a * 2
    Else
        Multiply = a * b
    End If
End Function

' Calling the function with one argument
WScript.Echo "Result: " & Multiply(5, Empty)

' Calling the function with two arguments
WScript.Echo "Result: " & Multiply(5, 3)

This example defines a function Multiply with an optional parameter b. If b is missing, it multiplies a by 2.

Recursive Function

Functions can call themselves, which is known as recursion.

recursive_function.vbs

Function Factorial(n)
    If n <= 1 Then
        Factorial = 1
    Else
        Factorial = n * Factorial(n - 1)
    End If
End Function

WScript.Echo "Factorial of 5: " & Factorial(5)

This example calculates the factorial of a number using recursion.

Function Returning an Array

Functions can return arrays.

array_function.vbs

Function GetNumbers()
    Dim nums(2)
    nums(0) = 10
    nums(1) = 20
    nums(2) = 30
    GetNumbers = nums
End Function

Dim result
result = GetNumbers()

WScript.Echo "Second number: " & result(1)

This example defines a function GetNumbers that returns an array.

Function with ByRef Parameter

VBScript allows passing parameters by reference using ByRef.

byref_function.vbs

Function Square(ByRef num)
    num = num * num
End Function

Dim x
x = 5
Square x

WScript.Echo "Square: " & x

This example defines a function Square that modifies the value of the parameter passed by reference.

Function Square(ByRef num)
    num = num * num
End Function

We use the ByRef keyword for the parameter.

Square x

Also, we must call he function without parentheses.

In this article, we explored how to create and use functions in VBScript. We covered simple functions, functions with multiple parameters, optional parameters, recursive functions, functions returning arrays, and functions with ByRef parameters. Functions are essential for writing modular and reusable code in VBScript.

Author

My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.

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