Question

Consider simple multiple select box

<select name="waste" id="waste" multiple>
<option value="5">garbage</option>
<option value="6">food</option>
<option value="8">Tin</option>
<option value="9">Can</option>
</select>

All it does is fire change event

$('#waste').change(function(){
//Inside here how will I know that this event was fired when user removed some values from selection 
// or did he added more values in selection
});

Answer 1

try this example : http://jsfiddle.net/7rf9J/

(function() {
    var s = $('#waste'),
      var  i = s.val().length;

    s.change(function(){
        var l = $(this).val().length;
        if (l === i) {
            console.log('you\'ve not changed selected value/s');   
        }
        else {
            if (l > i) {
                console.log('you inserted value/s');  
            }
            else {
                console.log('you removed value/s');             
            }
        }
        i = l;
    });
}());    

I’ve enclosed your function in an immediate self execute function in which I declared a variable containing the number of selected items. Every time you add o remove an item I save the current length of the value (initially set to 0), so you know if you added, removed or changed selection.