encounter a situation where you need to operate the first td, of each tr in table to do the click event 
 html like this 
<table class="datagrid-body">
  <tr>
    <td>Jill</td>
    <td>Smith</td> 
    <td>50</td>
  </tr>
  <tr>
    <td>Eve</td>
    <td>Jackson</td> 
    <td>94</td>
  </tr>
  <tr>
    <td>Eve</td>
    <td>Jackson</td> 
    <td>94</td>
  </tr>
</table>
 I currently write jquery like this, but only the td of the first tr has the click effect. 
 how can I make the first td of every tr eat this click effect? 
$(document).on("click", ".datagrid-body tr td:first", function (e){
    alert("test")
}});
