test.html

<!DOCTYPE html>
<html>
        <head>
                <title>localStorageEvent test</title>
                <script type="text/javascript">
                        function onstorage(event) {
                                alert([event.key, event.oldValue, event.newValue, event.url, event.storageArea].join('\n'));
                        }
                       
                        function insertValue() {
                                var value = prompt('Valeur :');
                                if(value)
                                        localStorage.setItem('data', value);
                        }
                       
                        function readValue() {
                                alert(localStorage.getItem('data'));
                        }
                       
                        window.onload = function() {
                                window.addEventListener('storage', onstorage, false);
                        }                                                                                                
                </script>
        </head>
        <body>
                <button onclick="insertValue();">Inserer une valeur</button>
                <br>
                <button onclick="readValue();">Lire la valeur</button>
        </body>
</html>