select2

HTML

<link rel="stylesheet" href="http://ivaynberg.github.com/select2/select2-3.3.1/select2.css">
<script src="http://ivaynberg.github.com/select2/select2-3.3.1/select2.js"></script>
<select id="select">
    <option selected>Selected</option>
    <option>Not selected</option>
</select>
<div id="console"></div>

CSS

body {
    font-family: sans-serif;
}

ul {
    padding: 0;
}

.info {
    color: #00f;
    font-weight: bold;
    font-size: 10px;
    float: right;
}

.info:hover {
    text-decoration: underline;
}

JavaScript

function onSelectChange(){
    alert('changed');
};

var select2 = $("#select").select2().data('select2');

select2.onSelect = (function(fn) {
    return function(data, options) {
        var target;
        
        if (options != null) {
            target = $(options.target);
        }
        
        if (target) {
            onSelectChange();
            return fn.apply(this, arguments);
        }
    }
})(select2.onSelect);