<!DOCTYPE html>
<html>
<head>
<script src="/lib/jquery-1.12.2.min.js"></script>
<script>
$(document).ready(function(){
$("button").click(function(){
$("input:text").val(function(n, c){
return c + " Griffin";
});
});
});
</script>
</head>
<body>
<p>Name: <input type="text" name="user" value="Peter"></p>
<button>Set the value of the input field</button>
</body>
</html>