<html>
<head>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
<script>
$(document).ready(function(){
$("input").keyup(function(){
var j = $("input").val();
if(j.length > 7)
{
var res = j.substring(0, 7);
$("input").val(res);
}
});
});
</script>
</head>
<body>
Enter your name: <input type="text">
</input></body>
</html>