Set colspan dynamically with jQuery

I have a simple table structure like this. What I would like to do is to dynamically merge some columns based on some condition within the <td> for example, if td1 and td3 are empty then merge the cells and do <td class="col1" colspan="3">1Meeting</td> I tried playing around with jQuery using:

 $(".tblSimpleAgenda  td:contains('')").hide();

but it had no effect.

What would be the the best way using jQuery to achieve this.

<table  class="tblSimpleAgenda" cellpadding="5" cellspacing="0">
 <tbody>
 <th align="left">Time</th>
 <th align="left">Room 1</th>
 <th align="left">Room 2</th>
 <th align="left">Room 3</th> 
    
        <tr valign="top">
            <td class="colTime">09:00 – 10:00</td>
            <td class="col1"></td>
            <td class="col2">Meeting 2</td>
            <td class="col3"></td>
        </tr>
        
        <tr valign="top">
            <td class="colTime">10:00 – 10:45</td>
            <td class="col1">Meeting 1</td>
            <td class="col2">Meeting 2</td>
            <td class="col3">Meeting 3</td> 
        </tr>
        
        <tr valign="top">
            <td class="colTime">11:00 – 11:45</td>
            <td class="col1">Meeting 1</td>
            <td class="col2">Meeting 2</td>
            <td class="col3">Meeting 3</td> 
        </tr>
</tbody>
</table>