<html><head><script src="https://libs.baidu.com/jquery/2.1.4/jquery.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>