VBScript

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VBScript

• Session 1

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Subjets for Session 1

• Vbscript fundamentals.
• Variant subtypes.
• Variables.
• Option Explicit statement.
• Keywords.
• Scope and liftime of variables.
• Dim, Private and Public statements.
• Rem statement.

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What is VBScript?

• A Safe subset of visual basic
• The VBScript Code is case Insensitive.
• Microsoft Visual Basic Scripting Edition brings
  active scripting to a wide variety of
  environments, including Web client scripting in
  Microsoft Internet Explorer and Web server
  scripting in Microsoft Internet Information
  Service (IIS).

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Microsoft Script Timeline
Version 1.0
Version 2.0
Version 3.0
Version 3.1
Version 4.0
Version 5.0
Internet Explorer 3.0 8/96
IIS 2 12/96
Internet Explorer 4.0 8/97
Windows 98
Visual Studio 6
Internet Explorer 5.0 Win NT 5.0
Note QuickTest uses VBScript 5.6
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Scripting for Specific Platforms

• VBScript
• designed to run on multiple platforms that use
  the ActiveX Scripting Interface.
• VBA (VB for Applications)
• More sophisticated customization.
• Power user focus, natural upgrade, superb
  integration
• Visual Basic
• Best tool for distributed client/Server
  solutions.
• Powerful, robust, scalable.

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VBScript Data Types

• VBScript has only one data type called a Variant.
  
• A Variant is a special kind of data type that can
  contain different kinds of information, depending
  on how it is used.
• Because Variant is the only data type in
  VBScript, it is also the data type returned by
  all functions in VBScript.
• At its simplest, a Variant can contain either
  numeric or string information.
• A Variant behaves as a number when you use it in
  a numeric context and as a string when you use it
  in a string context.

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VBScript Data Types Variant Subtypes

• Beyond the simple numeric or string
  classifications, a Variant can make further
  distinctions about the specific nature of numeric
  information.
• For example, you can have numeric information
  that represents a date or a time.
• When used with other date or time data, the
  result is always expressed as a date or a time.
• You can also have a rich variety of numeric
  information ranging in size from Boolean values
  to huge floating-point numbers.

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VBScript Data Types Variant Subtypes
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Variables

• A variable is a convenient placeholder that
  refers to a computer memory location where you
  can store program information that may change
  during the time your script is running.
• For example, you might create a variable called
  ClickCount to store the number of times a user
  clicks an object on a particular Web page.
• you only have to refer to a variable by his name
  to see or change its value.

x y z
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Declaring Variables

• You declare variables explicitly in your script
  using the Dim statement, the Public statement,
  and the Private statement. For example Dim
  DegreesFahrenheit
• You declare multiple variables by separating each
  variable name with a comma. For example
• Dim Top, Bottom, Left, Right

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Declaring Variables

• You can also declare a variable implicitly by
  simply using its name in your script.
• That is not generally a good practice because you
  could misspell the variable name in one or more
  places, causing unexpected results when your
  script is run.
• For that reason, the Option Explicit statement is
  available to require explicit declaration of all
  variables.

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Option Explicit Statement

• Forces explicit declaration of all variables in a
  script.
• If used, the Option Explicit statement must
  appear in a script before any other statements.
• When you use the Option Explicit statement, you
  must explicitly declare all variables using the
  Dim, Private, Public, or ReDim statements. If you
  attempt to use an undeclared variable name, an
  error occurs.
• Tip   Use Option Explicit to avoid incorrectly
  typing the name of an existing variable or to
  avoid confusion in code where the scope of the
  variable is not clear.

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Naming Restrictions

• Must begin with an alphabetic character.
• Cannot contain an embedded period.
• Must not exceed 255 characters.
• Must be unique in the scope in which it is
  declared.

Tip   meaningfull prefix to variables to indicate
the subtypes i.eiCounter (integer), strName
(String), bFlag (Boolean), dteToday (Date)
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VBScript Keywords

• Empty
• The Empty keyword is used to indicate an
  uninitialized variable value.
• Null
• The Null keyword is used to indicate that a
  variable contains no valid data.
• True
• The True keyword has a value equal to -1.
• False
• The False keyword has a value equal to 0.
• Nothing
• The Nothing keyword in VBScript is used to
  disassociate an object variable from any actual
  object.

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Scopes and Lifetimes

• A variable's scope is determined by where you
  declare it.
• When you declare a variable within a procedure,
  only code within that procedure can access or
  change the value of that variable.
• If you declare a variable outside a procedure,
  you make it recognizable to all the procedures in
  your script.
• The lifetime of a variable depends on how long it
  exists.
• The lifetime of a script-level variable extends
  from the time it is declared until the time the
  script is finished running.
• At procedure level, a variable exists only as
  long as you are in the procedure.
• ou can have local variables of the same name in
  several different procedures because each is
  recognized only by the procedure in which it is
  declared.

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Dim Statement

• Dim varname(subscripts), varname(subscripts
  ) . . .
• Declares variables and allocates storage space.
• Variables declared with Dim at the script level
  are available to all procedures within the
  script.
• At the procedure level, variables are available
  only within the procedure.
• You can also use the Dim statement with empty
  parentheses to declare a dynamic array.
• Note   When you use the Dim statement in a
  procedure, you generally put the Dim statement at
  the beginning of the procedure.

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Private Statement

• Private varname(subscripts),
  varname(subscripts) . . .
• Declares private variables and allocates storage
  space.
• Private statement variables are available only to
  the script in which they are declared.
• The following example illustrates use of the
  Private statement

Private MyNumber --- Private Variant variable.
Private MyArray(9) --- Private array variable.
--- Multiple Private declarations of Variant
variables. Private MyNumber, MyVar, YourNumber
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Public Statement

• Public varname(subscripts),
  varname(subscripts) . . .
• Declares public variables and allocates storage
  space.
• Public statement variables are available to all
  procedures in all scripts.
• You can also use the Public statement with empty
  parentheses to declare a dynamic array.

Public MyNumber --- Public Variant variable.
Public MyArray(9) --- Public array variable.
--- Multiple Public declarations of Variant
variables. Public MyNumber, MyVar, YourNumber
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Rem Statement

• Includes explanatory remarks in a program.
• Rem Comment
• Comment
• As shown in the syntax section, you can use an
  apostrophe (') instead of the Rem keyword.
• If the Rem keyword follows other statements on a
  line, it must be separated from the statements by
  a colon.
• However, when you use an apostrophe, the colon is
  not required after other statements.

MyStr1 "Hello" Rem Comment after a statement
separated by a colon. MyStr2 "Goodbye" ' This
is also a comment no colon is needed. Rem
Comment on a line with no code no colon is
needed.
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Assigning Values to Variables

• Values are assigned to variables creating an
  expression as follows
• the variable is on the left side of the
  expression and the value you want to assign to
  the variable is on the right.
• For Example

B 200
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Lab 1.1
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Lab 1.1

• Write a small program
• Declare using Dim 2 variables (a,b)
• Initialize the variables using a10 and b5
• Apply the sum to variable c.
• Report to QTP the sum of the variables.
• Use remarks.
• Tip Conversion
• Now declare in the header Option Explicit

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