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Editorial Team
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Asked: 2026-06-06T03:11:23+00:00

Let us say I have the following script, calculating a sum. Here is the

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Let us say I have the following script, calculating a sum.

Here is the code:

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

    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;

    }
    </script>

    </head>        
    <body>

    <?php

$tR = 1;
$maxlines = 5;

echo '<form name="form" method="post" action="action.php">';
echo '<table><tbody>';

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

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

    ?>

    </body>
    </html>

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:

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;

}
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1 Answer

  1. Editorial Team

    You can use a loop to go through all the fields:

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

        function updatesum() {
            var prices = document.getElementsByName('price');
            var numbers = document.getElementsByName('number');
            var sum = 0;

            for (var i = 0; i < prices.length; i++) {
                sum += prices[i].value * numbers[i].value;
            }
            document.form.sum.value = sum;
        }
        </script>
    </head>        
    <body>
        <?php
            $tR = 1;
            $maxlines = 50;

            echo '<form name="form" method="post" action="action.php">';
            echo '<table><tbody>';

            while($tR <= $maxlines)
            {
                echo '<tr>';
                echo '<td width="1"><input name="price" onChange="updatesum();"         type="text"></td>';
                echo '<td width="1"> x </td>';
                echo '<td width="1"><input name="number" onChange="updatesum();"         type="text" value="1"></td>';
                echo '</tr>';
                ++$tR;
            }
            echo '</tbody></table>';

            echo 'Total: <input name="sum" value="0" type="text" readonly="readonly">';
            echo '<button type="submit" name="Submit" style="display: hidden;">Submit</button>';
            echo '</form>';
        ?>
    </body>
</html>
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