How to get a table cell value using jQuery?

I am trying to work out how to get the value of table cell for each row using jQuery.

My table looks like this:

<table id="mytable">
  <tr>
    <th>Customer Id</th>
    <th>Result</th>
  </tr>
  <tr>
    <td>123</td>
    <td></td>
  </tr>
  <tr>
    <td>456</td>
    <td></td>
  </tr>
  <tr>
    <td>789</td>
    <td></td>
  </tr>
</table>

I basically want to loop through the table, and get the value of the Customer Id column for each row.

In the code below I have worked out that I need to do this to get it looping through each row, but I’m not sure how to get the value of the first cell in the row.

$('#mytable tr').each(function() {
    var cutomerId = 
}