VBScript Coding Conventions

Coding conventions are suggestions that may help you write code using Microsoft Visual Basic Scripting Edition. Coding conventions can include the following:

• Naming conventions for objects, variables, and procedures
• Commenting conventions
• Text formatting and indenting guidelines

The main reason for using a consistent set of coding conventions is to standardize the structure and coding style of a script or set of scripts so that you and others can easily read and understand the code. Using good coding conventions results in precise, readable, and unambiguous source code that is consistent with other language conventions and as intuitive as possible.

Earlier versions of VBScript had no mechanism for creating user-defined constants. Constants, if used, were implemented as variables and distinguished from other variables using all uppercase characters. Multiple words were separated using the underscore (_) character. For example:

 USER_LIST_MAX
 NEW_LINE

While this is still an acceptable way to indentify your constants, you may want to use an alternative naming scheme, now that you can create true constants using the Const statement. This convention uses a mixed-case format in which constant names have a "con" prefix. For example:

 conYourOwnConstant

For purposes of readability and consistency, use the following prefixes with descriptive names for variables in your VBScript code.

Subtype	Prefix	Example
Boolean	bln	blnFound
Byte	byt	bytRasterData
Date (Time)	dtm	dtmStart
Double	dbl	dblTolerance
Error	err	errOrderNum
Integer	int	intQuantity
Long	lng	lngDistance
Object	obj	objCurrent
Single	sng	sngAverage
String	str	strFirstName

Variables should always be defined with the smallest scope possible. VBScript variables can have the following scope.

Scope	Where Variable Is Declared	Visibility
Procedure-level	Event, Function, or Sub procedure	Visible in the procedure in which it is declared
Script-level	HEAD section of an HTML page, outside any procedure	Visible in every procedure in the script

Variable Scope PrefixesAs script size grows, so does the value of being able to quickly differentiate the scope of variables. A one-letter scope prefix preceding the type prefix provides this, without unduly increasing the size of variable names.

Scope	Prefix	Example
Procedure-level	None	dblVelocity
Script-level	s	sblnCalcInProgress

The body of a variable or procedure name should use mixed case and should be as complete as necessary to describe its purpose. In addition, procedure names should begin with a verb, such as InitNameArray or CloseDialog.

For frequently used or long terms, standard abbreviations are recommended to help keep name length reasonable. In general, variable names greater than 32 characters can be difficult to read. When using abbreviations, make sure they are consistent throughout the entire script. For example, randomly switching between Cnt and Count within a script or set of scripts may lead to confusion.

The following table lists recommended conventions for objects you may encounter while programming VBScript.

Object type	Prefix	Example
3D Panel	pnl	pnlGroup
Animated button	ani	aniMailBox
Check box	chk	chkReadOnly
Combo box, drop-down list box	cbo	cboEnglish
Command button	cmd	cmdExit
Common dialog	dlg	dlgFileOpen
Frame	fra	fraLanguage
Horizontal scroll bar	hsb	hsbVolume
Image	img	imgIcon
Label	lbl	lblHelpMessage
Line	lin	linVertical
List Box	lst	lstPolicyCodes
Spin	spn	spnPages
Text box	txt	txtLastName
Vertical scroll bar	vsb	vsbRate
Slider	sld	sldScale

All procedures should begin with a brief comment describing what they do. This description should not describe the implementation details (how it does it) because these often change over time, resulting in unnecessary comment maintenance work, or worse, erroneous comments. The code itself and any necessary inline comments describe the implementation.

Arguments passed to a procedure should be described when their purpose is not obvious and when the procedure expects the arguments to be in a specific range. Return values for functions and variables that are changed by a procedure, especially through reference arguments, should also be described at the beginning of each procedure.

Procedure header comments should include the following section headings. For examples, see the "Formatting Your Code" section that follows.

Section Heading	Comment Contents
Purpose	What the procedure does (not how).
Assumptions	List of any external variable, control, or other element whose state affects this procedure.
Effects	List of the procedure's effect on each external variable, control, or other element.
Inputs	Explanation of each argument that isn't obvious. Each argument should be on a separate line with inline comments.
Return Values	Explanation of the value returned.

Remember the following points:

• Every important variable declaration should include an inline comment describing the use of the variable being declared.
• Variables, controls, and procedures should be named clearly enough that inline comments are only needed for complex implementation details.
• At the beginning of your script, you should include an overview that describes the script, enumerating objects, procedures, algorithms, dialog boxes, and other system dependencies. Sometimes a piece of pseudocode describing the algorithm can be helpful.

Screen space should be conserved as much as possible, while still allowing code formatting to reflect logic structure and nesting. Here are a few pointers:

• Standard nested blocks should be indented four spaces.
• The overview comments of a procedure should be indented one space.
• The highest level statements that follow the overview comments should be indented four spaces, with each nested block indented an additional four spaces. For example:

 '*********************************************************
 ' Purpose:  Locates the first occurrence of a specified user
 '           in the UserList array.
 ' Inputs:   strUserList():   the list of users to be searched.
 '           strTargetUser:   the name of the user to search for.
 ' Returns:  The index of the first occurrence of the strTargetUser
 '           in the strUserList array.
 '           If the target user is not found, return -1.
 '*********************************************************

 Function intFindUser (strUserList(), strTargetUser)
     Dim i                     ' Loop counter.
     Dim blnFound	       ' Target found flag
     intFindUser = -1
     i = 0                     ' Initialize loop counter
     Do While i <= Ubound(strUserList) and Not blnFound
         If strUserList(i) = strTargetUser Then
             blnFound = True   ' Set flag to True
             intFindUser = i   ' Set return value to loop count
         End If
         i = i + 1             ' Increment loop counter
     Loop
 End Function