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VBScript Coding ConventionsĀ 

Coding conventions are suggestions are designed to 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 clear, precise, and readable source code that is consistent with other language conventions and is intuitive.

Constant Naming Conventions

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 identify 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

Variable Naming Conventions

To enhance 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

Variable Scope

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 Prefixes

As 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

Descriptive Variable and Procedure Names

The body of a variable or procedure name should use mixed case and should be as descriptive as necessary. 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.

Object Naming Conventions

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

Code Commenting Conventions

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 is not 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 to ensure 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.

Formatting Your Code

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

  • Indent standard nested blocks four spaces.

  • Indent the overview comments of a procedure one space.

  • Indent the highest level statements that follow the overview comments four spaces, with each nested block indented an additional four spaces.

The following code adheres to VBScript coding conventions.

'*********************************************************

' 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