VBScript

Last week I introduced you to functions and procedures within VBScript,

and the differences between the two. This week we create a function and

discuss the syntax.

To explain this topic, we need to define what our function will do.

Let's look at a very basic function that will take three numbers, add

them together and return a result to the calling line of code. Remember

that functions have the ability to return values, whereas procedures

cannot. Since our function needs to return a value, we need to define

it using the 'Function' keyword as opposed to the 'Sub' keyword.

Here is the code for the above example:

------------------- Begin code snippet -------------------

Dim Result, num1, num2, num3

num1 = 3

num2 = 4

num3 = 5

Result = add(num1, num2, num3)

WScript.Echo(num1 & " + " & num2 & " + " & num3 & " = " & Result)

'Function to add 3 numbers together

Function add(num1, num2, num3)

Dim tempResult

tempResult = num1 + num2 + num3

add = tempResult

End Function

-------------------- End code snippet --------------------

If you copy the above code snippet into a text file, save it as

c:\scripts\functions.vbs, open a command prompt and then type the

following:

cscript c:\scripts\functions.vbs

you will see the following output:

------------------- Begin output -------------------

Microsoft (R) Windows Script Host Version 5.6

Copyright (C) Microsoft Corporation 1996-2001. All rights reserved.

3 + 4 + 5 = 12

--------------------- End Output -------------------

Let's step through the code to see what is happening. In the first part

of our script we define 3 variables (num1, num2, and num3) and assign

each of them a value. Next we call our function and assign the return

value from the function to the variable 'Result'. At this point the

script jumps to the code for the function and execution continues within

the function. Looking at the function, we see that it accepts three

parameters (numA, numB, and numC). Since we called our function with

the call 'Result = add(num1, num2, num3)', the function assigns the

three new variables as follows:

numA = num1

numB = num2

numC = num3

So now the function can manipulate numA, numB, and numC without

impacting the original variables num1, num2, and num3. The function

then takes the three variables, adds them together, and assigns the

result to tempResult. Now, the second to last line of code in this

function is key to the usage of functions. The statement is 'add =

tempResult', which basically tells the your script to have the 'add'

function return a value equal to the value contained in the variable

'tempResult'. In this case the value is '12'. Now when we hit the line

that says 'End Function' our function terminates and the program control

is returned to the calling line of code which was 'Result = add(num1,

num2, num3)'. Now since the 'add' function returned a value to this

section of code, you can actually picture this line to look like 'Result

= 12', and then the code continues from there and displays the result in

the format we have specified.

As you can see, functions and their counterpart, procedures, are a very

useful features in VBScript.

Next week we will begin discuss a discussion on error handling withing

VBScript.

What’s wrong? The new clean desk test
Join the discussion
Be the first to comment on this article. Our Commenting Policies