1 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.

2 VBScripting To include a control use input tags. – To have VBScript recognized by the browser - use the following: –

3 VBScripting contd. To build the command button for the Input tag: – –<!-- –Sub cmdButton_OnClick Msgbox ”Please enter a number from 1 to 10." –End Sub

4 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

5 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

6 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

7 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

8 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

9 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

10 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

11 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

12 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

13 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

14 Message Box Buttons vbOKOnly Shows only the OK button vbOkCancel Shows the OK and Cancel buttons vbAbortRetryIgnore Shows the Abort, Retry and Ignore buttons vbYesNoCancel Shows the Yes, No and Cancel buttons vbYesNo Shows the Yes and No buttons vbRertyCancel Shows the Retry and Cancel buttons

15 Message Box Parameters vbCritical Uses a Critical X as an indicator vbQuestion Uses a Question mark as an indicator vbExclamation Uses a Exclamation point as an indicator vbInformation Uses an I as an indicator

16 Message Box Return Codes vbOk -1 - Indicates an OK status vbCancel Indicates a return of cancel vbAbort Indicates a return of abort vbRetry Indicates a return of retry vbIgnore Indicates a return of Ignore vbYes Indicates a return of yes vbNo Indicates a return of No

17 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.

18 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

19 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

20 Conditional Statements If ( condition) Then – statements ElseIf (condition) Then – statements Else – statements End If All data types must be of the same type

21 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

22 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

23 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

24 Case Statements Multiple If tests (nested or otherwise) can be replaced with the Case Statement It is easier to read and easier to construct

25 Case Statement contd. Select Case expression – Case Is relational expression Statement – Case Constant To Constant Statement – [Case Else] Statement End Select

26 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

27 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.

28 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