Edit in JSFiddle

// helper function for displaing results
var output = function(result) {
    document.getElementById('output').innerHTML = result;
}

window.addEventListener('storage', function(e){
    output(
        "Old values: {'" + e.key +"':'"+ e.oldValue +"'}<br/>" +
        "New values: {'" + e.key +"':'"+ e.newValue +"'}"
    );
});

Result: <span id="output"></span>
 

span {
    color: #f00;
}