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<h1>VBScript Looping Statements</h1>
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<h2>Examples</h2>
<p>
<a target="_blank" href="tryit.asp@filename=vbdemo_fornext">For...next loop</a><br />
This example demonstrates how to make a simple <b>For....Next</b> loop.
</p>
<p>
<a target="_blank" href="tryit.asp@filename=vbdemo_fornext2">Looping through headers</a><br />
This example demonstrates how you can loop through the 6 headers in html.
</p>
<p>
<a target="_blank" href="tryit.asp@filename=vbdemo_foreach">For...each loop</a><br />
This example demonstrates how to make a simple <b>For.....Each</b> loop.
</p>
<p>
<a target="_blank" href="tryit.asp@filename=vbdemo_dowhile">Do...While loop</a><br />
This example demonstrates how to make a simple <b>Do...While</b> loop.
</p>
<hr />
<h2>Looping Statements</h2>
<p>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.</p>
<p>In VBScript we have four looping statements:</p>
<ul>
<li><b>For...Next statement </b>- runs statements a specified number of times. </li>
<li><b>For Each...Next statement </b>- runs statements for each item in a collection or each element of an array</li>
<li><b>Do...Loop statement </b>- loops while or until a condition is true</li>
<li><b>While...Wend statement </b>- Do not use it - use the Do...Loop statement instead</li>
</ul>
<hr />
<h2>For...Next Loop</h2>
<p>
You can use a <b>For...Next</b> statement to run a block of code, when you know how many repetitions you want.
</p>
<p>
You can use a counter variable that increases or decreases with each repetition of the loop, like this:
</p>
<table width="100%" border="1" class="ex" cellspacing="0"><tr><td>
<pre>For i=1 to 10
some code
Next</pre>
</td></tr></table>
<p>The <b>For</b> statement specifies the counter variable (<b>i</b>) and its start and end
values. The <b> Next</b> statement increases the counter variable (<b>i</b>) by one.</p>
<h3>Step Keyword</h3>
<p>
Using the <b> Step</b> keyword, you can increase or decrease the counter variable by the value you specify.
</p>
<p>
In the example below, the counter variable (<b>i</b>) is increased by two each time the loop repeats.
</p>
<table width="100%" border="1" class="ex" cellspacing="0"><tr><td>
<pre>For i=2 To 10 Step 2
some code
Next</pre>
</td></tr></table>
<p>
To decrease the counter variable, you must use a negative <b> Step</b> value. You must specify
an end value that is less than the start value.
</p>
<p>
In the example below, the counter variable (<b>i</b>) is decreased by two each time the loop repeats.
</p>
<table width="100%" border="1" class="ex" cellspacing="0"><tr><td>
<pre>For i=10 To 2 Step -2
some code
Next</pre>
</td></tr></table>
<h3>Exit a For...Next</h3>
<p>You can exit a For...Next statement with the Exit For keyword.</p>
<hr />
<h2>For Each...Next Loop</h2>
<p>
A <b>For Each...Next</b> loop repeats a block of code for each item in a collection, or for each element of an array.
</p>
<table width="100%" border="1" class="ex" cellspacing="0"><tr><td>
<pre>dim cars(2)
cars(0)="Volvo"
cars(1)="Saab"
cars(2)="BMW"
For Each x in cars
document.write(x & "<br />")
Next</pre>
</td></tr></table>
<br />
<hr />
<h2>Do...Loop</h2>
<p>
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.
</p>
<h3>Repeating Code While a Condition is True</h3>
<p>
You use the While keyword to check a condition in a Do...Loop statement.
</p>
<table width="100%" border="1" class="ex" cellspacing="0"><tr><td>
<pre>Do While i>10
some code
Loop</pre>
</td></tr></table>
<p>If <b> i</b> equals 9, the code inside the loop above will never be executed.</p>
<table width="100%" border="1" class="ex" cellspacing="0"><tr><td>
<pre>Do
some code
Loop While i>10</pre>
</td></tr></table>
<p>
The code inside this loop will be executed at least one time, even if <b> i</b> is less than 10.
</p>
<h3>Repeating Code Until a Condition Becomes True</h3>
<p>
You use the Until keyword to check a condition in a Do...Loop statement.
</p>
<table width="100%" border="1" class="ex" cellspacing="0"><tr><td>
<pre>Do Until i=10
some code
Loop</pre>
</td></tr></table>
<p>
If <b> i</b> equals 10, the code inside the loop will never be executed.
</p>
<table width="100%" border="1" class="ex" cellspacing="0"><tr><td>
<pre>Do
some code
Loop Until i=10</pre>
</td></tr></table>
<p>The code inside this loop will be executed at least one time, even if <b> i</b> is equal to 10.</p>
<h3>Exit a Do...Loop</h3>
<p>
You can exit a Do...Loop statement with the Exit Do keyword.
</p>
<table width="100%" border="1" class="ex" cellspacing="0"><tr><td>
<pre>Do Until i=10
i=i-1
If i<10 Then Exit Do
Loop</pre>
</td></tr></table>
<p>
The code inside this loop will be executed as long as <b> i</b> is different
from 10, and as long as <b> i</b> is greater than 10.
</p>
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