In order to write VBScript, you have to know how to structure your code so that your scripts and programs execute properly. Each of the different types of VBScript that you write has different rules regarding its structure. We'll look at each of these in turn. We'll also examine the ways in which your host environment allows you to import VBScript code libraries, thus allowing you to create reusable code. Finally, we'll end the chapter with a discussion of VBScript usage to write class modules. First, though, it's important to cover the basic structures of VBScript that are relevant to all of the different script types: that script-level code calls code in individual functions or procedures.

Functions and Procedures

Functions and procedures (or subroutines) are central to modern programming. Dividing our script into subroutines helps us to maintain and write programs by segregating related code into smaller, manageable sections. It also helps to reduce the number of lines of code we have to write by allowing us to reuse the same subroutine or function many times in different situations and from different parts of the program. In this section, we'll examine the different types of subroutines, how and why they are used, and how using subroutines helps to optimize code.

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Introduction

Defining Subroutines: The Sub . . . End Sub Construct

Calling a Subroutine

Passing Variables into a Subroutine

Exiting a Routine with the Exit Statement

The Class Construct, Variables, Properties, Methods and Events

The Script Level: Active Server Pages

Windows Script Host

Client-Side Scripts for MSIE

Outlook Forms

Reusable Code Libraries: Active Server Pages