1 <input type="text" placeholder="请输入您的用户名...">
 2 <script type="text/javascript">
 3         $("input[name=‘username‘]").bind(‘input‘,function(){
 4             var pattern = new RegExp("[^a-zA-z1-9]");
 5             var rs = ‘‘;
 6             var str = $(this).val();
 7 
 8             for (var i=0;i< str.length;++i){
 9                 rs = rs + str.substr(i, 1).replace(pattern,‘‘);
10             }
11 
12             $(this).val(rs);
13         });
14 </script>