Web Programming Overview

1
Web Programming Overview

• HTML
• Hypertext Markup Language
• DHTML
• Dynamic Hypertext Markup Language
• Any kind of coding that changes the behavior of a
  web page based on user response
• Client-side programming run in client browser
• Server-side programming run on web server
• XML
• EXtensible Markup Language
• Data and data formatting standard

2
Client-Side Programming

• Written in Javascript,VB Script or other
  languages
• Fast because doesnt have to communicate with
  server
• Often used for data validation or data formatting
• Generally less secure than server-side
• Demo
• http//www.purdue.anderson.edu/Cpt/Courses/Cpt255/
  Quiz.htm
• View source to see Javascript

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What is VBScript?

• VBScript (also known as Visual Basic Scripting
  Edition) is a lightweight programming language
  that is designed to run inside web pages and
  other applications.
• VBScript can be used for both client-side and
  server-side programming.
• VBScript is a scaled down version of Visual
  Basic.
• Visual Basic for Applications (VBA) - a subset of
  Visual Basic that is optimized for use with
  Microsoft Access and other Microsoft Office
  applications.
• VBScript is optimized for use in web browsers,
  especially Internet Explorer.

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Placing Client-side Vbscript In Web Pages

• Script Blocks
• Runat"client" optional but best practice
• Can place blocks in body to be run as page is
  displayed
• Can place blocks in head functions and sub
  procedures

ltSCRIPT LANGUAGE"VBScript" runat"client"gt
Option Explicit Public Sub WriteALine(What2Write
) Document.Write(What2Write) Document.write("lt
BR /gt") End Sub lt/scriptgt
example1.htm
5
VBScript Variables

• A memory location holding data that can be
  accessed or changed at a later time while the
  program is running
• All variables are variant datatype
• hold either text or numbers
• Behave as a number when you use them in a numeric
  context and as text when you use them in a text
  context

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VBScript Variables (cont)

• Do not have to be explicitly declared
• Unless use Option Explicit
• But requiring explicit declaration is best
  practice
• Declare variables with Dim, Private, or Public
  followed by the variable name
• Public variables are available to all procedures
  in all scripts in current page
• Private variables are available only to the
  script in which they are declared
• Dim variables
• (at script level) are available everywhere within
  the script
• (at procedure level) are available only within
  procedure

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VBScript Variables (cont)

• Naming
• Must begin with an alphabetic character
• Cannot contain a period
• Cannot exceed 255 characters
• Must be unique within its scope

8
VBScript Arrays

• An array is a set of variables conveniently
  packages for easy handling
• Dim Emp(5)
• One dimensional
• Dim Emp (5,3)
• Two dimensional
• Dim Emp()ReDim Emp(x)
• Dynamic dimensioning

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VBScript Constants

• Similar to a variable except that its value never
  changes
• Usefulness
• In reviewing code a constant name can be more
  meaningful than the number which is its value
• The value of the constant can be changed in one
  place
• Declaration
• Const cSalesTax .05

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Select Case
Syntax Select Case testexpression Case
expressionlist-n statements-n . . .
Case Else expressionlist-n
elsestatements-n End Select Example Select
Case grade Case "A" Document.Write("Excellent")
Case "B" Document.Write("Good") End Select
example2.htm
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If-Then-Else
Syntax If condition Then statements ElseIf
condition-n Then elseifstatements . .
. Else elsestatements End If Example If
grade gt 89 Then Document.Write("Excellent") Else
Document.Write("Good") End If
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Do Loop
Syntax Do While Until condition
statements Exit Do Loop Examples poweroftw
o 2 Do While poweroftwo lt1000 Document.Write(po
weroftwo) Document.Write("ltBR /gt") poweroftwo
poweroftwo 2 Loop
poweroftwo 2 Do Document.Write(poweroftwo
) Document.Write("ltBR /gt") poweroftwo
poweroftwo 2 Loop While poweroftwo lt1000
With Do Loop While Until, loop will be
processed at least once
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For-Next Loop
Syntax For counter Start To End Step
stepvalue statements Exit
For Next Examples For i 1 to
10 Document.Write(i) Document.Write("ltBR
/gt") Next
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For Each -Next Loop
Syntax For Each element In group statements
Exit For Next element Examples For Each
Item In Document.MyForm.Elements Document.Write(I
tem.Name) Document.write(" ") Document.Write(I
tem.Value) Document.write("ltBR /gt") Next
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Selected Built-in Formatting Functions
16
Selected Built-in Math Functions
17
Selected Built-in String Functions
18
Selected Built-in Date Functions
19
Date FunctionTime Intervals
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Selected Built-in Data Conversion Functions
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Selected Built-in Misc Functions
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Calling Built-in Functions
ltSCRIPT LANGUAGE"VBScript" runat"client"gt
Option Explicit Dim currentdate currentdate
Now Document.Write("The current date and time is
") Document.Write(currentdate) Document.Write("ltbr
/gt") Document.Write ("The current date is
") Document.Write(FormatDateTime(currentdate,
vbShortDate)) Document.Write("ltbr
/gt") Document.Write ("The current (24 hour) time
is ") Document.Write(FormatDateTime(currentdate,
vbShortTime)) Document.Write("ltbr
/gt") Document.Write("This time next week, it will
be ") Document.Write(DateAdd("d",7,currentdate))
Document.Write("ltbr /gt") lt/scriptgt
See example1.htm
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Sub Procedures
Syntax Public Default Private SubName
(arguments) statements Exit Sub
statements End Sub Example Public Sub
WriteALine(What2Write) Document.Write(What2Write
) Document.write("ltBR /gt") End Sub Example of
Calling a Sub Call SubName(argument1,
argument2) SubName argument1, argument2
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User-written Functions
Syntax Public Default Private FunctionName
(arguments) statements FunctionName
expression Exit Function statements End
Sub Example Public Function Square(Number)
Square Number Number End Sub Example of
Calling a Function x Square(13)
Document.Write(Square(13))
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Passing Variables ByVal and ByRef

• ByVal (default) indicates that the value of the
  variable is passed but not the variable itself.
  The sub or function works with a copy of the
  variable.
• ByRef indicates that the variable itself is
  passed and that changes made to the value of the
  variable inside the sub or function will also
  change the value of the variable outside the
  routine.

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ByRef vs. ByVal
Private Sub ChangeValues(ByVal X, ByRef
Y) xx2 yy2 End Sub
ltbodygt ltSCRIPT LANGUAGE"VBScript"
runat"client"gt Option Explicit Dim x,
y x10 y20 Call ChangeValues(x,y) Document.Write(
x "ltBR /gt") Document.Write(y "ltBR
/gt") lt/scriptgt lt/bodygt
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Client-side VBScript Form Validation

• User entries on forms can be validated on either
  client-side or server-side
• Client-side validation is more immediate
• Client-side JavaScript is more universal
• Client-side VBScript uses Form_OnSubmit function
• Automatically called
• Sets function to True or False
• False cancels the form action

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Client-side VBScript Form Validation
ltSCRIPT LANGUAGE"VBScript" runat"client"gt
Option Explicit Private Function
MyForm_OnSubmit MyForm_OnSubmit True If
(Document.MyForm.First.Value) "" Then
MsgBox("First Name field blank. Please enter your
first name.") MyForm_OnSubmit False End
If If IsNumeric(Document.MyForm.First.Value)
True Then MsgBox("You typed a number. Please
enter your first name.") MyForm_OnSubmit
False End If If MyForm_OnSubmit True
Then MsgBox("Hello, " Document.MyForm.First.Val
ue) End If End Function lt/scriptgt
Example3.htm
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Practice

• In Class Workshop
• Review Exercise 3 (exercise3.htm)
• Write code for Exercise 1
• Assignment
• Write code for Exercise 4
• Due Sept 3
• Also, read Chapter 13 14