Visual Basic Keywords Included in VB Script

By Rick Darnell

VBScript includes all the keywords and features that you need to activate a Web page. You can't read or write files, as you'll learn later in this appendix, but you can handle any event that an object fires. You can also handle just about any type of data that you'll find on a Web page and manipulate the Web page in anyway you want.

Table C.1 describes each keyword or feature available in VBScript. I've divided this table into broad categories, with each entry under a category describing a single feature. I've used the same categories that Microsoft uses so that you can keep this information straight as you bounce back and forth between Microsoft's Web site and this book. If you don't find a feature that you expect to see, check out Table C.2 to see if that feature is in the list of Visual Basic features omitted from VBScript.

You can find more information about VBScript's features at Microsoft's VBScript Web site: http://www.microsoft.com/vbscript.

Table C.1  VBScript Keywords

Keyword/Feature Description
Array handling
IsArray Returns True if a variable is an array
Erase Reinitilizes a fixed-size array
LBound Returns the lower bound of an array
UBound Returns the upper bound of an array
Assignments
= Assigns a value to a variable
Let Assigns a value to a variable
Set Assigns an object to a variable
Comments
` Includes inline comments in your script
Rem Includes comments in your script
Constants/Literals
Empty Indicates an uninitialized variable
Nothing Disassociates a variable with an object
Null Indicates a variable with no data
True Boolean True
False Boolean False
Control flow
Do...Loop Repeats a block of statements
For...Next Repeats a block of statements
For Each...Next Repeats a block of statements
If...Then...Else Conditionally executes statements
Select Case Conditionally executes statements
While...Wend Repeats a block of statements
Conversions
Abs Returns absolute value of a number
Asc Returns the ASCII code of a character
AscB Returns the ASCII code of a character
AscW Returns the ASCII code of a character
Chr Returns a character from an ASCII code
ChrB Returns a character from an ASCII code
ChrW Returns a character from an ASCII code
CBool Converts a variant to a boolean
CByte Converts a variant to a byte
CDate Converts a variant to a date
CDbl Converts a variant to a double
Cint Converts a variant to an integer
CLng Converts a variant to a long
CSng Converts a variant to a single
CStr Converts a variant to a string
DateSerial Converts a variant to a date
DateValue Converts a variant to a date
Hex Converts a variant to a hex string
Oct Converts a variant to an octal string
Fix Converts a variant to a fixed string
Int Converts a variant to an integer string
Sgn Converts a variant to a single string
TimeSerial Converts a variant to a time
TimeValue Converts a variant to a time
Dates/Times
Date Returns the current date
Time Returns the current time
DateSerial Returns a date from its parts
DateValue Returns a date from its value
Day Returns day from a date
Month Returns month from a date
Weekday Returns weekday from a date
Year Returns year from a date
Hour Returns hour from a time
Minute Returns minute from a time
Second Returns seconds from a time
Now Returns current date and time
TimeSerial Returns a time from its parts
TimeValue Returns a time from its value
Declarations
Dim Declares a variable
Private Declares script-level private variable
Public Declares public-level public variable
ReDim Reallocates an array
Function Declares a function
Sub Declares a subprocedure
Error Handling
On Error Enables error handling
Err Contains information about last error
Input/Output
InputBox Prompts the user for input
MsgBox Displays a message to the user
Math
Atn Returns the Arctangent of a number
Cos Returns the cosine of a number
Sin Returns the sine of a number
Tan Returns the tangent of a number
Exp Returns the exponent of a number
Log Returns the logarithm of a number
Sqr Returns the square root of a number
Randomize Reseeds the randomizer
Rnd Returns a random number
Operators
+ Addition
- Subtraction
^ Exponentiation
Mod Modulus arithmetic
* Multiplication
/ Division
\ Integer Division
- Negation
& String concatenation
= Equality
<> Inequality
< Less Than
<= Less Than or Equal To
> Greater Than
>= Greater Than or Equal To
Is Compares expressions
And Compares expressions
Or Compares expressions
Xor Compares expressions
Eqv Compares expressions
Imp Compares expressions
Objects
CreateObject Creates reference to an OLE object
IsObject Returns True if object is valid
Options
Option Explicit Forces explicit variable declaration
Procedures
Call Invokes a subprocedure
Function Declares a function
Sub Declares a subprocedure
Strings
Instr Returns index of a string in another
InStrB Returns index of a string in another
Len Returns the length of a string
LenB Returns the length of a string
Lcase Converts a string to lowercase
Ucase Converts a string to uppercase
Left Returns the left portion of a string
LeftB Returns the left portion of a string
Mid Returns the mid portion of a string
MidB Returns the mid portion of a string
Right Returns the right portion of a string
RightB Returns the right portion of a string
Space Pads a string with spaces
StrComp Compares two strings
String Pads a string with a character
Ltrim Removes leading spaces from a string
Rtrim Removes trailing spaces from a string
Trim Removes leading and trailing spaces
Variants
IsArray Returns True if variable is an array
IsDate Returns True if variable is a date
IsEmpty Returns True if variable is empty
IsNull Returns True if variable is null.
IsNumeric Returns True if variable is a number
IsObject Returns True if variable is an object
VarType Indicates a variable's type

Visual Basic Keywords Omitted from VBScript

VBScript leaves out a bunch of Visual Basic keywords such as DoEvents, Print, and Shell. You can't read or write files, either, and you can't do much graphical programming. This won't stop you from creating great Web pages with VBScript, though, because VBScript provides every feature you need to do just about anything you want on the Web page. For example, you can dynamically change the contents of the Web page itself and you can interact with every object on the Web page.

Don't look at the list of omitted keywords and features yet. You need to understand why Microsoft didn't include them so that you'll understand why each feature is on this list. Take a look:

  • Portability  Microsoft intends to make VBScript available on a variety of platforms including Windows, Mac, UNIX, and so on. They've wisely removed keywords and features that make VBScript less portable to these platforms.

  • Performance  You've heard it before: speed or features--pick one. Microsoft removed many nonessential features from VBScript so scripts load and run faster.

  • Safety  You should be concerned with security on the Internet. You don't want to open a Web page and discover that it contains a script which crashes your drive, do you? Microsoft removed any Visual Basic feature that might cause a security problem with scripts such as file I/O. You can still get access to these features, however, if you create an ActiveX object which you control with VBScript.

Table C.1 describes each keyword or feature available in Visual Basic but omitted from VBScript. I've divided this table into broad categories, with each entry under a category describing a single feature. I've used Microsoft's categories so that you can keep the list on Microsoft's Web site in sync with this list.


NOTE: The Internet Explorer Script Error dialog box tells you that it found a statement in your script which couldn't interpret. I'm sure that you've seen error messages such as "Expected while or until" or nested comments that just don't make any sense. When VBScript encounters a keyword it doesn't recognize, it spews out all sorts of garbage like the previous example. It usually points to the offending keyword, however, by placing a caret (^) directly underneath it. The next time you get one of these unexplained errors, look up the keyword in Table C.2 to see if Microsoft omitted it from VBScript.

© Copyright Macmillan Computer Publishing. All rights reserved.

Make a Comment

Loading Comments...

  • Web Development Newsletter Signup

    Invalid email
    You have successfuly registered to our newsletter.
  •