Javascript - How to get one or two selected checkbox into database

i need to get one or max three selected checkbox that i can insert into database, and also i have a id jumlah that i need to input and calculate it (jumlah*harga) show it on id hasil.

This is the jumlah * harga i tried, this is success

 function sum(id) {
  var harga = document.getElementById('harga-' + id).value;
  var jumlah = document.getElementById('jumlah-' + id).value;
  var hasil = parseInt(harga) * parseInt(jumlah);
   if (!isNaN(hasil)) 
      {
         document.getElementById('total-' + id).value = hasil;
       }
}

but i want, i can calculate this when i select the checkbox

This is the foreach loop

@foreach($ob as $b)
<tr>
  <td>
      <input type="checkbox" name="select" id="check" value=">
  </td>
  <td> 
      <input name="jumlah" id="jumlah" onkey="sum()">
  </td>
  <td>
     <input name="harga" id="harga" onkey="sum()">
  </td>
  <td>
      <input name="hasil" id="hasil" onkey="sum()">
  </td>
</tr>
@endforeach

I need to get the selected checkbox row as data not array