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Scripting Languages

• VBScript - Recognized mainly by Internet Explorer only - Netscape does have a plug-in

• JavaScript - Recognized by Internet Explorer and Netscape

• Perl - Used at the server side• Server v.s. Client programming• VBScript is similar to VB programming, but uses

a subset of the language.

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VBScripting

• To include a control use input tags.– <INPUT TYPE=BUTTON NAME=cmdButton

VALUE="Click Here">

• To have VBScript recognized by the browser - use the following:– <SCRIPT LANGUAGE="VBScript">– <!-- Use comment tag so that browsers that do not

support VBScript will not print the code -->– </SCRIPT>

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VBScripting contd.

• To build the command button for the Input tag:– <SCRIPT LANGUAGE="VBScript">– <!-- – Sub cmdButton_OnClick

• Msgbox ”Please enter a number from 1 to 10."

– End Sub

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Data - Variables & Constants

• Constant is data that will not change - fixed in value

• Variable is data that can change during the course of the running of a program

• Identifier is a name assigned to a variable or constant - memory is reserved for the variable / constant

• Declaration statements define the variable / constant for the program

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Declaration Statements

• Const Identifier [As Datatype] = Value• Const is a reserved word to define a constant in

the declaration section• Dim Identifier [As Datatype]• A defaulted datatype becomes type variant• String values are called string literals• Intrinsic constants are VB built-in constants

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Data Types

• Boolean - True or False value (0 or 1)• Byte - A single ASCII character• Single & Currency - Floating Point • Date - An eight character date• Double - Double precision floating point • Long & Integer - Whole number• String - Alphanumeric characters• Variant - Stores any type

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Local Declarations

• The Dim statement can be placed anywhere within the local procedure

• It is recommended to be placed at the top of the procedure

• It must be placed before the variable is used• Variables and constants can be declared locally

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Arithmetic Operators

• The order of precedence is as follows:– Exponentiation - [^]– Multiplication and Division - [*, /]– Addition and Subtraction - [+, -]

• Use parenthesis to change evaluation order of a mathematical expression

• All evaluations occur from left to right• Parenthesis are performed first then in the order

of precedence

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Arrays

• A series of items (Data Types) that are related to one another

• They use the same name with an index to each part (element) of the array

• They are similar to a control array except they are for data storage

• The name tables or subscripted variables is sometimes used with them

• The index is the subscript of the array

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Dimensioning Arrays

• The Dim statement is used similar to all other declarations

• Dim Arrayname ([lower To] Upper) [As Datatype]

• The lower subscript is not necessary - if left out the lower subscript will be zero

• The datatype may be left out and defaults to variant

• All data elements are initialized to zero for numerics and null string for strings

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Dynamic Arrays

• Arrays can be dimensioned dynamically• An array declared as - Dim Name() As Integer• Will allow redimensioning during program

execution• The Redim statement is used to rediminsion an

array• All other arrays are static arrays

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Array Subscripts

• The subscript used to reference into the array can be a constant

• A literal number• A variable• A numeric expression• The subscript MUST reference a valid element

of the array

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Message Boxes

• Message Boxes are used to notify the user of an error or display information

• The message box can contain a message, icon, title bar caption or command button

• MsgBox “message” [,buttons/icon][, “title bar”] • Displays the message centered in box• Displays title bar caption in the title bar

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Message Box Buttons

• vbOKOnly - 0 - Shows only the OK button

• vbOkCancel - 1 - Shows the OK and Cancel buttons

• vbAbortRetryIgnore - 2 - Shows the Abort, Retry and Ignore buttons

• vbYesNoCancel - 3 - Shows the Yes, No and Cancel buttons

• vbYesNo - 4 - Shows the Yes and No buttons

• vbRertyCancel - 5 - Shows the Retry and Cancel buttons

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Message Box Parameters

• vbCritical - 16 - Uses a Critical X as an indicator

• vbQuestion - 32 - Uses a Question mark as an indicator

• vbExclamation - 48 - Uses a Exclamation point as an indicator

• vbInformation - 64 - Uses an I as an indicator

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Message Box Return Codes

• vbOk -1 - Indicates an OK status

• vbCancel - 2 - Indicates a return of cancel

• vbAbort - 3 - Indicates a return of abort

• vbRetry - 4 - Indicates a return of retry

• vbIgnore - 5 - Indicates a return of Ignore

• vbYes - 6 - Indicates a return of yes

• vbNo - 7 - Indicates a return of No

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Procedures / Functions

• A sub procedure is code that performs a given operation, but does not return anything.

• A function is code that performs a given operation and then returns a value to the caller. This value can be the result of some operation or just an error code.

• The returned value is accomplished by using the name of the function and assigning a value.

• To exit a sub procedure prematurely use Exit Sub.

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Functions

• Functions perform an action and return a value associated with that action

• The VAL function will convert data into a numeric format

• The Val function converts until the first non-numeric character is read

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System Procedures

• There are two types of system classes.– Events - a subroutine executed automatically by the

system when a certain event takes place.• OnBlur - executed when an object is deselected

• OnChange - executed when a user changes the object

• OnClick - executed when an object is clicked

• OnFocus - executed when an object is active (user selects)

– Methods - controlled events. Methods normally are used to cause something to occur.

• Calling a method is done by using the object name and the method name.

• Objectname.Methodname

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Conditional Statements

• If ( condition) Then– statements

• ElseIf (condition) Then– statements

• Else– statements

• End If• All data types must be of the same type

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Relational Operators

• The relational operators are used to compare two values - the result of the comparison is either True or False

• > - Greater than• < - Less than• = - Equal to• <> - not equal to• >= - Greater than or equal to• <= - Less than or equal to

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Conditional Statements contd.

• ASCII comparisons, handled left to right • All string literals must be enclosed in double

quotes• Be careful using text boxes - their data type is

variant• To check uppercase characters - Ucase()• To check lowercase characters - Lcase()• Use logical operators to test multiple conditions -

Or , And , Not, Xor, Equ, Imp

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Conditional statements contd.

• Nested If Statements can be used, just remember to include the End If inside the nested If

• The nesting can be accomplished in the Then portion of the condition, or in the Else portion

• The ElseIf statement or an If within an If are both valid statements

• It is highly recommended to flowchart conditional statements

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Case Statements

• Multiple If tests (nested or otherwise) can be replaced with the Case Statement

• It is easier to read and easier to construct

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Case Statement contd.

• Select Case expression– Case Is relational expression

• Statement

– Case Constant To Constant• Statement

– [Case Else]• Statement

• End Select

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Do Loops

• Do Loops repeat instructions until a condition is met

• Do While condition– statements to be repeated

• Loop• Do

– statements to be repeated• Loop Until condition

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For / Next Loops

• Used to allow repetitive operations in a sequence of code.

• For LoopIndex = Startvalue To EndValue [Step Increment]– statements to be repeated

• Next LoopIndex

• The Loop Index must be declared before entering the loop and the end value must be attainable.

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For / Next Loops contd.

• Once the end value has been reached the execution will drop out of the loop.

• Negative numbers are allowed for the step value

• Altering the values of the control variables will not affect the operation of the loop