Hi I have the following code for appending comboboxes when button is clicked.

I want to check if the value is selected in any previous combobox if it is selected then alert "value is already selected".

For example, I have 5 comboboxes appended and the value in each combobox should be different from each other by traversing each value in the comboboxes:

<div class="custom-control custom-checkbox">
  <input type="checkbox" class="itemRow custom-control-input" id="itemRow_1">
  <label class="custom-control-label" for="itemRow_1"></label>
</div>

<div class="form-group has-success">
  <select name="proid[]" class="form-control" id="proid_1" required="required">
  </select>                                                     
</div>

<div class="form-group has-success">
  <button type="button" name="addbtn" id="addbtn" class="btn btn-success">Add Product</button>
</div>

JQUERY CODE

var count = $(".itemRow").length;

$(document).on('click', '#addbtn', function() {
  count++;
  var productcombo='';
  productcombo += '<tr>';
  productcombo +='<td><input type="checkbox" class="custom-control-input itemRow" id="itemRow_'+count+'"> <label class="custom-control-label" for="itemRow_'+count+'"></label> </td>';
  productcombo +='<td><select name="proid[]" class="form-control" id="proid_'+count+'" required="required"> </select></td>';
  productcombo += '</tr>'; 
  $('#products').append(productcombo);
});

$("#proid_"+count).change(function() 
{
  var id = $(this).find(":selected").val();

  // code here to compare each value 
  if(value found in previous comboboxes)
  {
    alert("Already Selected");
  }
});