Microsoft® Visual Basic® Scripting Edition
VBScript Coding Conventions
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Coding conventions are suggestions that may help you write code using Microsoft Visual Basic Scripting Edition. Coding conventions can include the following:
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.
- Naming conventions for objects, variables, and procedures
- Commenting conventions
- Text formatting and indenting guidelines
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: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:USER_LIST_MAX NEW_LINEconYourOwnConstant
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.
Remember the following points:
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.
- 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