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Get Client IP Address 

    <script type="text/javascript" src="http://l2.io/ip.js">
        $(document).ready(function () {
            $.getJSON("http://smart-ip.net/geoip-json?callback=?",
            function (json) {
                alert(json.ip); // alerts the ip address       
            });
        });
    </script>

Reference:http://stackoverflow.com/questions/391979/get-client-ip-using-just-javascript