Question

 <table width="600px" id='testTable'>
        <tr class="red"><td>this</td></tr>
        <tr><td>1</td></tr>
        <tr><td>1</td></tr>
        <tr><td>1</td></tr>
        <tr class="red"><td>1</td></tr>
        <tr><td>1</td></tr>
        <tr><td>1</td></tr>
        <tr class="red"><td>this</td></tr>
        <tr><td>1</td></tr>
        <tr><td>1</td></tr>
        <tr class="red"><td>1</td></tr>
        <tr><td>1</td></tr>
        <tr><td>1</td></tr>
    </table>


.gray
{
    background-color:#dddddd;
}
.red
{
    color:Red;
}

    $(function () {
        $('#testTable tr.red:nth-child(odd)').addClass('gray');
       //this should select tr's with text=this, but its not happening
    });

i want to select all odds inside table which have class=red , but its not happening. please help

Answer 1

nth-child(odd) selects the odd members of the element’s parent not the odd members of the set returned by the selector.

You’re looking for this:

$('#testTable tr.red').filter(':even').addClass('gray');

Edit: actually you want the even ones, i think. It’s a 0-based index. Demo