LOOPING THROUGH CODE

Looping statements are used to run the same block of code a specified number of times.
In VBScript  four looping statements are available :
  • For...Next statement - runs code a specified number of times
  • For Each...Next statement - runs code 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:

·         Use the For...Next statement to run a block of code a specified number of times.
·         The For statement specifies the counter variable (i), and its start and end values. The Next statement increases the counter variable (i) by one.

Example
·         <html>
<body>
<%
For i = 0 To 10
  response.write("The number is " & i & "<br />")
Next
%>
</body>
</html>

 The Step Keyword:

With the Step keyword, we can increase or decrease the counter variable by the value we specify.

Example:

 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,  use a negative Step value. Specify an end value that is less than the start value.

Example:

 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:

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

For i=1 To 10
  If i=5 Then Exit For
  some code
Next

For Each...Next Loop:

For Each...Next loop repeats a block of code for each item in a collection, or for each element of an array.
Example:
<html>
<body>
<%
Dim colors(2)
cars(0)="green"
cars(1)="blue"
cars(2)="red"
For Each x In colors
  response.write(x & "<br />")
Next
%>
</body>
</html>

Do...Loop:

If we don't know how many repetitions we want, use a Do...Loop statement.
The Do...Loop statement repeats a block of code while a condition is true, or until a condition becomes true.

Repeat Code While a Condition is True

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

Do While i>100
  some code
Loop

If i equals 99, the code inside the loop above will never be executed.

Do
  some code
Loop While i>100

The code inside this loop will be executed at least one time, even if i is less than 100.

Repeat Code Until a Condition Becomes True

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

Do Until i=100
  some code
Loop

If i equals 100, the code inside the loop will never be executed.

Do
  some code
Loop Until i=100

The code inside this loop will be executed at least one time, even if i is equal to 10.

Exit a Do...Loop

we can exit a Do...Loop statement with the Exit Do keyword.

Do Until i=100
  i=i-1
  If i<10 Then Exit Do
Loop

The code inside this loop will be executed as long as i is different from 10, and as long as i is greater than 10.

While...Wend statement :

In a While..Wend loop, if the condition is True, all statements are executed until Wend keyword is encountered.
If the condition is false, the loop is exited and the control jumps to very next statement after Wendkeyword.

Syntax:

The syntax of a While..Wend loop in VBScript is:
While condition(s)
   [statements 1]
   [statements 2]
   ...
   [statements n]
Wend



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