实现对数据的校验并提示

 1 <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
 2 <html xmlns="http://www.w3.org/1999/xhtml">
 3 <head>
 4 <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
 5 <title>无标题文档</title>
 6 </head>
 7 
 8 <body>
 9 <div align="center">
10     <table>
11         <tr>
12             <td>用户名：</td><td><input onfocus="ffocus()" onblur="bblur(this)" type="text" id="uerName"/></td><td id="mess" ></td>
13         </tr>
14     
15     </table>
16 
17 </div>
18 </body>
19 <script>
20     function ffocus(){
21         document.getElementById("mess").innerHTML="用户名必须是3-6个字符";
22     
23     }
24     function bblur(t){
25         var userName=t.value;
26         alert(userName.length);
27         if(userName.length>=3&&userName.length<=6){
28             document.getElementById("mess").innerHTML="<img width='100px' height='50px' src='正确.png' >";
29         
30         }else{
31             document.getElementById("mess").innerHTML="<img width='100px' height='50px' src='错误.png' >";
32         
33         }
34         
35     }
36 </script>
37 </html>