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>
<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
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
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:
A 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>
<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
Loop
If i equals 99, the code inside the loop
above will never be executed.
Do
some code
Loop While i>100
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
some code
Loop
If i equals 100, the code inside the loop
will never be executed.
Do
some code
Loop Until i=100
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
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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