<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<script>
$(function() {
$("button").on("click", { key: "val" }, function(e) {
alert(e.data.key)
});
});
</script>
</head>
<body>
<button>GO</button>
</body>
</html>