<html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> <title></title> <script src="http://www.cnblogs.com/scripts/jquery-1.3.1.js" type="text/javascript"></script> <script type="text/javascript"> $(function(){ $("#sub").bind("click",function(event){ var username = $("#username").val(); //获取元素的值 if(username==""){ //判断值是否为空 $("#msg").html("<p>文本框的值不能为空.</p>"); //提示信息 return false; } }) }) </script> </head> <body> <form action="test.html"> 用户名：<input type="text" id="username" /> <br/> <input type="submit" value="提交" id="sub"/> </form> <div id="msg"></div> </body> </html>