html table column summation

<table width="200" border="0" id="table">

  <tr>

    <td>Name</td>

    <td>Image</td>

    <td>Price</td>

    <td>操作</td><table width="200" border="0" id="table">

  <tr>

    <td>Name</td>

    <td>Image</td>

    <td>Price</td>

    <td>操作</td>

  </tr>

  <tr>

    <td> </td>

    <td> </td>

    <td>10</td>

    <td> </td>

  </tr>

  <tr>

    <td> </td>

    <td> </td>

    <td>10</td>

    <td> </td>

  </tr>

  <tr>

    <td> </td>

    <td> </td>

    <td>10</td>

    <td> </td>

  </tr>

  <tr>

    <td> </td>

    <td> </td>

    <td>10</td>

    <td> </td>

  </tr>

  <tr>

    <td> </td>

    <td>Total</td>

    <td> </td>

    <td> </td>

  </tr>

</table>

<script type="text/javascript">

    var calcTotal=function(table,column){//Total, table object, which column is to be totaled, the first column starts from 0

        var trs=table.getElementsByTagName('tr');

        var start=1,//Ignore the header of the first line

            end=trs.length-1;//Ignore the last total line

        var total = 0;

        for(var i=start;i<end;i++){

            var td=trs[i].getElementsByTagName('td')[column];

            var t = parseFloat (td.innerHTML);

            if(t)total+=t;

        }

        trs[end].getElementsByTagName('td')[column].innerHTML=total;

    };

    calcTotal(document.getElementById('table'),2);

</script>