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VB Script
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Subjects forSession
Vbscript fundamentals.
Variant subtypes.
Variables.
Option Explicitstatement.
Keywords.
Scope and liftime of variables.
Dim, Privateand Publicstatements.
Remstatement.
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What is VBScript?
A Safe subset of visual basic
The VBScript ode is case !nsensitive.
"icrosoft Visual Basic Scriptin# $dition brin#sactive scriptin# to a wide variety of environments,includin# Web client scriptin# in "icrosoft !nternet$%plorer and Web server scriptin# in "icrosoft!nternet !nformation Service &!!S'.
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"icrosoft( Script Timeline
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!nternet
$%plorer ).*+-
Version/.* Version0.*
!!S 0/0-
!nternet$%plorer 1.*
+-2
Version).*
Windows-+
Version)./ Version1.*Version3.*
VisualStudio !nternet$%plorer 3.*
Win 4T 3.*
4ote5 6uic7Test uses VBScript 3.
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Scriptin# for Speci8c 9latforms
VBScript
: desi#ned to run on multiple platforms that use theActive; Scriptin# !nterface.
VBA &VB for Applications': "ore sophisticated customi
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VBScript has only one data type called a Variant.
A Variantis a special 7ind of data type that cancontain di=erent 7inds of information, dependin# onhow it is used.
Because Variantis the only data type in VBScript, itis also the data type returned by all functions inVBScript.
At its simplest, a Variantcan contain either numericor strin# information.
A Variantbehaves as a number when you use it in anumeric conte%t and as a strin# when you use it in astrin# conte%t.
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VBScript >ata TypesVariant Subtypes
Beyond the simple numeric or strin# classi8cations, aVariantcan ma7e further distinctions about thespeci8c nature of numeric information.
or e%ample, you can have numeric information thatrepresents a date or a time.
When used with other date or time data, the result isalways e%pressed as a date or a time.
@ou can also have a rich variety of numeric informationran#in# in si
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VBScript >ata TypesVariant Subtypes
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Subtype Description
$mpty Variantis uninitiali
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Variables
A variable is a convenient placeholder that refers to acomputer memory location where you can storepro#ram information that may chan#e durin# thetime your script is runnin#.
or e%ample, you mi#ht create a variable calledlic7ount to store the number of times a user clic7san obHect on a particular Web pa#e.
you only have to refer to a variable by his name to
see or chan#e its value.
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>eclarin# Variables
@ou declare variables e%plicitly in your script usin# theDimstatement, the Publicstatement, and the Privatestatement. or e%ample5
Dim>e#reesahrenheit
@ou declare multiple variables by separatin# eachvariable name with a comma. or e%ample5
DimTop, Bottom, Deft, Ii#ht
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>eclarin# Variables
@ou can also declare a variable implicitly bysimply usin# its name in your script.
That is not #enerally a #ood practice because
you could misspell the variable name in one ormore places, causin# une%pected results whenyour script is run.
or that reason, the Option Explicitstatement is available to reJuire e%plicit
declaration of all variables.
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Gption $%plicit Statement
orces e%plicit declaration of all variables in a script.
!f used, the OptionExplicitstatement must appearin a script before any other statements.
When you use the OptionExplicitstatement, youmust e%plicitly declare all variables usin# the Dim,Private, Public, or ReDimstatements. !f youattempt to use an undeclared variable name, an erroroccurs.
Tip se OptionExplicitto avoid incorrectly typin#the name of an e%istin# variable or to avoid confusionin code where the scope of the variable is not clear.
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"ust be#in with an alphabetic character.
annot contain an embedded period.
"ust not e%ceed 033 characters.
"ust be uniJue in the scope in which it is
declared.
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Tip meanin#full pre8% to variables to indicate thesubtypes i.eiounter &inte#er', str4ame &Strin#', bla# &Boolean',dteToday &>ate'
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$mpty: The Empty7eyword is used to indicate an uninitiali
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A variableLs scope is determined by where you declare it.
When you declare a variable within a procedure, only code within thatprocedure can access or chan#e the value of that variable.
!f you declare a variable outside a procedure, you ma7e it reco#ni
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DimvarnameM!MsubscriptsN"NM# varnameM!MsubscriptsN"NN $ $ $
>eclares variables and allocates stora#e space.
Variables declared with Dimat the script level are available to allprocedures within the script.
At the procedure level, variables are available only within the
procedure.
@ou can also use the Dimstatement with empty parentheses todeclare a dynamic array.
Note When you use the Dimstatement in a procedure, you
#enerally put the Dimstatement at the be#innin# of the
procedure.
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PrivatevarnameM!MsubscriptsN"NM# varnameM!MsubscriptsN"NN $ $ $
>eclares private variables and allocates stora#e space.
9rivate statement variables are available only to the script in whichthey are declared.
The followin# e%ample illustrates use of the Privatestatement5
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Private"y4umber 9rivate Variant variable.Private"yArray&-' 9rivate array variable. "ultiple 9rivate declarations of Variant variables.Private"y4umber, "yVar, @our4umber
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PublicvarnameM!MsubscriptsN"NM# varnameM!MsubscriptsN"NN $ $ $
>eclares public variables and allocates stora#e space.
Publicstatement variables are available to all procedures inall scripts.
@ou can also use the Publicstatement with emptyparentheses to declare a dynamic array.
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Public"y4umber 9ublic Variant variable.Public"yArray&-' 9ublic array variable.
"ultiple 9ublic declarations of Variant variables.
Public"y4umber, "yVar, @our4umber
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