VBScript Coding Conventions

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


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