JSFiddle - React, Tailwind, and code Playground

HTML

<select rel="prop216" name="prop[]">
<option value="">- none</option>
<option value="12">Opt 1</option>
<option value="13">Opt 2</option>
</select>
<select rel="prop217" name="prop[]">
<option value="">- none</option>
<option value="12">Opt 1</option>
<option value="13">Opt 2</option>
</select>

JavaScript

$("select").change(function()
{ 
    var i = 0;
    var alteredSelects = [];
    $("select").each(function() 
    { 
        if ( $(this).val() !== "" ) 
        {
            alteredSelects[i][0] = $(this).attr('rel'); 
            alteredSelects[i][1] = $(this).val();
            alert ($(this).attr('rel'));
            i++;
            
        }
    }); 
});