Dynamically add table row and calculate total

http://www.sitepoint.com/forums/showthread.php?1199613-Show-running-total-from-dynamic-amount-of-text-boxes

by hibbard_eu

HTML

<table>
    <tr>
        <td>Amount</td>
    </tr>
    <tr class="row_to_clone">
        <td>
            <input type="text" name="amount" value="" class="txt" autocomplete='off' />
        </td>
    </tr>
    <tr class="row_to_clone">
        <td>
            <input type="text" name="amount" value="" class="txt" autocomplete='off' />
        </td>
    </tr>
</table>
<a class="addRow" href="#">Add Another Row</a>

<div>Sum: <span id="sum"></span></div>

JavaScript

function addRow() {
    /* Declare variables */
    var elements, templateRow, rowCount, row, className, newRow, element;
    var i, s, t;

    /* Get and count all "tr" elements with class="row".    The last one will
     * be serve as a template. */
    if (!document.getElementsByTagName) return false; /* DOM not supported */
    elements = document.getElementsByTagName("tr");
    templateRow = null;
    rowCount = 0;
    for (i = 0; i < elements.length; i++) {
        row = elements.item(i);

        /* Get the "class" attribute of the row. */
        className = null;
        if (row.getAttribute) className = row.getAttribute('class')
        if (className == null && row.attributes) { // MSIE 5
            /* getAttribute('class') always returns null on MSIE 5, and
             * row.attributes doesn't work on Firefox 1.0.    Go figure. */
            className = row.attributes['class'];
            if (className && typeof (className) == 'object' && className.value) {
                // MSIE 6
                className = className.value;
            }
        }

        /* This is not one of the rows we're looking for.    Move along. */
        if (className != "row_to_clone") continue;

        /* This *is* a row we're looking for. */
        templateRow = row;
        rowCount++;
    }
    if (templateRow == null) return false; /* Couldn't find a template row. */

    /* Make a copy of the template row */
    newRow = templateRow.cloneNode(true);

    /* Change the form variables e.g. price[x] -> price[rowCount] */
    elements = newRow.getElementsByTagName("input");
    for (i = 0; i < elements.length; i++) {
        element = elements.item(i);
        s = null;
        s = element.getAttribute("name");
        if (s == null) continue;
        t = s.split("[");
        if (t.length < 2) continue;
        s = t[0] + "[" + rowCount.toString() + "]";
        element.setAttribute("name", s);
        element.value = "";
    }
    
    /* Remove any pre-existing...