Topic: Detail Description About VBScript?

Message

What is VBScript? 

VBScript is a scripting language
A scripting language is a lightweight programming language
VBScript is a light version of Microsoft's programming language Visual Basic

What is VBScript? 

VBScript is a scripting language
A scripting language is a lightweight programming language
VBScript is a light version of Microsoft's programming language Visual Basic

How Does it Work?

When
a VBScript is inserted into a HTML document, the Internet browser will
read the HTML and interpret the VBScript. The VBScript can be executed
immediately, or at a later event.

How to Put VBScript Code in an HTML Document

<html>
<head>
</head>
<body>
<script type="text/vbscript">
document.write("Hello from VBScript!")
</script>
</body>
</html>
And it produces this output:

Hello from VBScript!

To insert a script in an HTML document, use the <script> tag. Use the type attribute to define the scripting language.

<script type="text/vbscript">
Then comes the VBScript: The command for writing some text on a page is document.write: 

document.write("Hello from VBScript!")
The script ends:

</script>

How to Handle Older Browsers

Older
browsers that do not support scripts will display the script as page
content. To prevent them from doing this, you can use the HTML comment
tag:

<script type="text/vbscript">
<!--
  some statements
-->
</script>

Head section

Scripts can be placed in the head section. Usually
we put all the "functions" in the head section. The reason for this is
to be sure that the script is loaded before the function is called.

Body section

Execute a script that is placed in the body section. Scripts in the body section are executed when the page is loading.

Where to Put the VBScript

Scripts
in a page will be executed immediately while the page loads into the
browser. This is not always what we want. Sometimes we want to execute
a script when a page loads, other times when a user triggers an event.

Scripts in the head section:
Scripts to be executed when they are called or when an event is
triggered go in the head section. When you place a script in the head
section you will assure that the script is loaded before anyone uses
it:

<html>
<head>
<script type="text/vbscript">
  some statements
</script>
</head>
Scripts in the body section:
Scripts to be executed when the page loads go in the body section. When
you place a script in the body section it generates the content of the
page:

<html>
<head>
</head>
<body>
<script type="text/vbscript">
  some statements
</script>
</body>
Scripts in both the body and the head section: You can place an unlimited number of scripts in your document, so you can have scripts in both the body and the head section.

<html>
<head>
<script type="text/vbscript">
  some statements
</script>
</head>
<body>
<script type="text/vbscript">
  some statements
</script>
</body>

Examples

Create a variable

Variables are used to store information. This example demonstrates how you can create a variable, and assign a value to it.

Insert a variable value in a text

This example demonstrates how you can insert a variable value in a text.

Create an array

Arrays are used to store a series of related data
items. This example demonstrates how you can make an array that stores
names. ( We are using a "for loop" to demonstrate how you write the
names. )

What is a Variable?

A
variable is a "container" for information you want to store. A
variable's value can change during the script. You can refer to a
variable by name to see its value or to change its value. In VBScript,
all variables are of type variant, that can store different types of data. 

Rules for Variable Names:

Must begin with a letter 
Cannot contain a period (.)
Cannot exceed 255 characters

Declaring Variables

You can declare variables with the Dim, Public or the Private statement. Like this: 

dim name
name=some value
Now you have created a variable. The name of the variable is "name".

You can also declare variables by using its name in your script. Like this:

name=some value
Now you have also created a variable. The name of the variable is "name".

However,
the last method is not a good practice, because you can misspell the
variable name later in your script, and that can cause strange results
when your script is running. This is because when you misspell for
example the "name" variable to "nime" the script will automatically
create a new variable called "nime".  To prevent your script from doing
this you can use the Option Explicit statement. When you use this
statement you will have to declare all your variables with the dim,
public or private statement. Put the Option Explicit statement on the
top of your script. Like this:

option explicit
dim name
name=some value

Assigning Values to Variables

You assign a value to a variable like this:

name="Hege"
i=200
The
variable name is on the left side of the expression and the value you
want to assign to the variable is on the right. Now the variable "name"
has the value "Hege".

Lifetime of Variables

How long a variable exists is its lifetime.

When you declare a variable within a procedure, the variable can
only be accessed within that procedure. When the procedure exits, the
variable is destroyed. These variables are called local variables. You
can have local variables with the same name in different procedures,
because each is recognized only by the procedure in which it is
declared.

If you declare a variable outside a procedure, all the procedures
on your page can access it. The lifetime of these variables starts when
they are declared, and ends when the page is closed.

Array Variables

Sometimes
you want to assign more than one value to a single variable. Then you
can create a variable that can contain a series of values. This is
called an array variable. The declaration of an array variable uses
parentheses ( ) following the variable name. In the following example,
an array containing 3 elements is declared:

dim names(2)
The
number shown in the parentheses is 2. We start at zero so this array
contains 3 elements. This is a fixed-size array. You assign data to
each of the elements of the array like this:

names(0)="Tove"
names(1)="Jani"
names(2)="Stale"
Similarly, the data can be retrieved from any element using the index of the particular array element you want. Like this:

mother=names(0)
You
can have up to 60 dimensions in an array. Multiple dimensions are
declared by separating the numbers in the parentheses with commas. Here
we have a two-dimensional array consisting of 5 rows and 7 columns:

dim table(4, 6)

Examples

Sub procedure

The sub procedure does not return a value.

Function procedure

The function procedure is used if you want to return a value.

VBScript Procedures

We have two kinds of procedures: The Sub procedure and the Function procedure.

A Sub procedure:

is a series of statements, enclosed by the Sub and End Sub statements
can perform actions, but does not return a value
can take arguments that are passed to it by a calling procedure
without arguments, must include an empty set of parentheses ()

Sub mysub()
 some statements
End Sub
or

Sub mysub(argument1,argument2)
 some statements
End Sub 
A Function procedure:

is a series of statements, enclosed by the Function and End Function statements
can perform actions and can return a value
can take arguments that are passed to it by a calling procedure
without arguments, must include an empty set of parentheses ()
returns a value by assigning a value to its name

Function myfunction()
 some statements
 myfunction=some value
End Function
or

Function myfunction(argument1,argument2)
 some statements
 myfunction=some value
End Function

Call a Sub or Function Procedure

When you call a Function in your code, you do like this:

name = findname()
Here you call a Function called "findname", the Function returns a value that will be stored in the variable "name".

Or, you can do like this:

msgbox "Your name is " & findname()
Here you also call a Function called "findname", the Function returns a value that will be displayed in the message box.

When you call a Sub procedure you can use the Call statement, like this:

Call MyProc(argument)
Or, you can omit the Call statement, like this:

MyProc argument

Examples

The if...then...else statement

This example demonstrates how to write the if...then..else statement.

The if...then...elseif... statement

This example demonstrates how to write the if...then...elseif statement.

The select case statement

This example demonstrates how to write the select case statement.

Conditional Statements

Very
often when you write code, you want to perform different actions for
different decisions. You can use conditional statements in your code to
do this.

In VBScript we have three conditional statements:

if statement - use this statement if you want to execute a set of code when a condition is true
if...then...else statement - use this statement if you want to select one of two sets of lines to execute
if...then...elseif statement - use this statement if you want to select one of many sets of lines to execute
select case statement - use this statement if you want to select one of many sets of lines to execute

If....Then.....Else

You should use the If...Then...Else statement if you want to

execute some code if a condition is true
select one of two blocks of code to execute

If you want to execute only one statement when a condition is true, you can write the code on one line:

if i=10 Then msgbox "Hello"
There is no ..else.. in this syntax. You just tell the code to perform one action if the condition is true (in this case if i=10).

If you want to execute more than one
statement when a condition is true, you must put each statement on
separate lines and end the statement with the keyword "End If":

if i=10 Then
   msgbox "Hello"
   i = i+1
end If
There is no ..else.. in this syntax either. You just tell the code to perform multiple actions if the condition is true.

If
you want to execute a statement if a condition is true and execute
another statement if the condition is not true, you must add the "Else"
keyword:

if i=10 then
   msgbox "Hello"
else
   msgbox "Goodbye"
end If
The
first block of code will be executed if the condition is true, and the
other block will be executed otherwise (if i is not equal to 10).

If....Then.....Elseif

You can use the if...then...elseif statement if you want to select one of many blocks of code to execute:

if payment="Cash" then
   msgbox "You are going to pay cash!"
 elseif payment="Visa" then
   msgbox "You are going to pay with visa."
 elseif payment="AmEx" then
   msgbox "You are going to pay with American Express."
 else
   msgbox "Unknown method of payment."
end If

Select Case

You can also use the SELECT statement if you want to select one of many blocks of code to execute:

select case payment
 case "Cash"
   msgbox "You are going to pay cash"
 case "Visa"
   msgbox "You are going to pay with visa"
 case "AmEx"
   msgbox "You are going to pay with American Express"
 case Else
   msgbox "Unknown method of payment"
end select
This
is how it works: First we have a single expression (most often a
variable), that is evaluated once. The value of the expression is then
compared with the values for each Case in the structure. If there is a
match, the block of code associated with that Case is executed.

Examples

For...next loop

This example demonstrates how to make a simple For....Next loop.

Looping through headers

This example demonstrates how you can loop through the 6 headers in html.

For...each loop

This example demonstrates how to make a simple For.....Each loop.

Do...While loop

This example demonstrates how to make a simple Do...While loop.

Looping Statements

Very
often when you write code, you want to allow the same block of code to
run a number of times. You can use looping statements in your code to
do this.

In VBScript we have four looping statements:

For...Next statement - runs statements a specified number of times. 
For Each...Next statement - runs statements for each item in a collection or each element of an array
Do...Loop statement - loops while or until a condition is true
While...Wend statement - Do not use it - use the Do... 
Loop statement instead

For...Next 
Loop

You can use a For...Next statement to run a block of code, when you know how many repetitions you want.

You can use a counter variable that increases or decreases with each repetition of the loop, like this:

For i=1 to 10
  some code
Next
The For statement specifies the counter variable (i) and its start and end values. The Next statement increases the counter variable (i) by one.

Step Keyword

Using the Step keyword, you can increase or decrease the counter variable by the value you specify.

In the example below, the counter variable (i) is increased by two each time the loop repeats.

For i=2 To 10 Step 2
  some code
Next
To decrease the counter variable, you must use a negative Step value. You must specify an end value that is less than the start value.

In the example below, the counter variable (i) is decreased by two each time the loop repeats.

For i=10 To 2 Step -2
  some code
Next
Exit a For...Next

You can exit a For...Next statement with the Exit For keyword.

For Each...Next 
Loop

A For Each...Next loop repeats a block of code for each item in a collection, or for each element of an array.

dim cars(2)
cars(0)="Volvo"
cars(1)="Saab"
cars(2)="BMW"

For Each x in cars
  document.write(x & "<br />")
Next

Do...Loop

You can use Do...
Loop
statements to run a block of code when you do not know how many
repetitions you want. The block of code is repeated while a condition
is true or until a condition becomes true.

Repeating Code While a Condition is True

You use the While keyword to check a condition in a Do...
Loop statement.

Do While i>10
  some code
Loop
If i equals 9, the code inside the loop above will never be executed.

Do
  some code
Loop While i>10
The code inside this loop will be executed at least one time, even if i is less than 10.

Repeating Code Until a Condition Becomes True

You use the Until keyword to check a condition in a Do...
Loop statement.

Do Until i=10
  some code    
Loop
If i equals 10, the code inside the loop will never

Edited by Mithi25 - 27Oct2009 at 11:53pm


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Topic: Detail Description About VBScript?

What is VBScript?

What is VBScript?

How Does it Work?

How to Put VBScript Code in an HTML Document

How to Handle Older Browsers

Where to Put the VBScript

Examples

What is a Variable?

Rules for Variable Names:

Declaring Variables

Assigning Values to Variables

Lifetime of Variables

Array Variables

Examples

VBScript Procedures

Call a Sub or Function Procedure

Examples

Conditional Statements

If....Then.....Else

If....Then.....Elseif

Select Case

Examples

Looping Statements

For...Next Loop

Step Keyword

Exit a For...Next

For Each...Next Loop

Do...Loop

Repeating Code While a Condition is True

Repeating Code Until a Condition Becomes True