HTML
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
$(".dosomething").click(function(){
$(".deftext").val($(this).attr("my_title"));
});
});
</script>
</head>
<body>
<input class="deftext" value="Fred" > <br>
<button class="dosomething" my_title="Stupid Face">OK</button>
</body>
</html>
