<select name="sono[]" id="sonoDetails" class="select2 form-control select2-hidden-accessible" tabindex="-1" aria-hidden="true">
    <option value="">Select SO No</option>
    <option value="5" data-bookingtime="2015-10-16 21:00:00">5</option>
    <option value="4" data-bookingtime="2015-10-17 20:15:00">4</option>
</select>

$(document).ready(function(){
    $(".select2").select2();
    $(document).on("change","select[name='sono[]']",function(){//
        var me = $(this);
        var sono = me.select2("val");
          console.log(sono);
    });
 });

$(document).ready(function(){
    $(".select2").select2().on("change", function (e) {
        console.log("change",$(this).val());
    });
});

var bindsonoSelect = function(){
        $("select#sonoDetails").on("change",function(){
            var me = $(this);
             var sono = me.select2("val");
            //var sono = me.select2().val();
            console.log(sono);
        }
    });
 }
bindsonoSelect ();