Creating a loop in Javascript based on php variable
<p>Let us say I have the following script, calculating a sum.</p>

<p>Here is the code:</p>

<pre><code>    &lt;html&gt;
    &lt;head&gt;
    &lt;meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /&gt;
    &lt;script language="javascript" type="text/javascript"&gt;

    function updatesum() {

    line1 = ((document.form.price_1.value -0) * (document.form.number_1.value -0));

    line2 = ((document.form.price_2.value -0) * (document.form.number_2.value -0));

    line3 = ((document.form.price_3.value -0) * (document.form.number_3.value -0));

    line4 = ((document.form.price_4.value -0) * (document.form.number_4.value -0));

    line5 = ((document.form.price_5.value -0) * (document.form.number_5.value -0));

    document.form.sum.value = line1 + line2 + line3 + line4 + line5;

    }
    &lt;/script&gt;

    &lt;/head&gt;        
    &lt;body&gt;

    &lt;?php

$tR = 1;
$maxlines = 5;

echo '&lt;form name="form" method="post" action="action.php"&gt;';
echo '&lt;table&gt;&lt;tbody&gt;';

while($tR &lt;= $maxlines)
{
echo '&lt;tr&gt;';
echo '&lt;td width="1"&gt;&lt;input name="price_' . $tR . '" onChange="updatesum();"         type="text"&gt;&lt;/td&gt;';
echo '&lt;td width="1"&gt; x &lt;/td&gt;';
echo '&lt;td width="1"&gt;&lt;input name="number_' . $tR . '" onChange="updatesum();"         type="text" value="1"&gt;&lt;/td&gt;';
echo '&lt;/tr&gt;';
++$tR;
}
echo '&lt;/tbody&gt;&lt;/table&gt;';

echo 'Total: &lt;input name="sum" value="0" type="text" readonly="readonly"&gt;';
echo '&lt;button type="submit" name="Submit" style="display: hidden;"&gt;Submit&lt;/button&gt;';
echo '&lt;/form&gt;';

    ?&gt;

    &lt;/body&gt;
    &lt;/html&gt;
</code></pre>

<p>And that's fine... But now i change the variable $maxlines from 5 to 500...
How do I adjust the Javascript, without having to write something like:</p>

<pre><code>function updatesum() {

line1 = ((document.form.price_1.value -0) * (document.form.number_1.value -0));

line2 = ((document.form.price_2.value -0) * (document.form.number_2.value -0));

line3 = ((document.form.price_3.value -0) * (document.form.number_3.value -0));

line4 = ((document.form.price_4.value -0) * (document.form.number_4.value -0));

line5 = ((document.form.price_5.value -0) * (document.form.number_5.value -0));

line6 = ((document.form.price_6.value -0) * (document.form.number_6.value -0));

  .......................

line500 = ((document.form.price_500.value -0) * (document.form.number_500.value -0));

document.form.sum.value = line1 + line2 + line3 + line4 + line5 + line6 ........... + line500;

}
</code></pre>
