无刷新验证表单

 1 <script type="text/javascript">
 2   function checklogin1(){
 3     if(document.login1.username.value=="" || document.login1.username.value.replace(/s/g,'')==''){
 4       alert('请输入用户名！');
 5       document.login1.username.focus();
 6       return false;
 7     }else if(document.login1.password.value==""){
 8       alert('请输入密码！');
 9       document.login1.password.focus();
10       return false;
11     }else if(document.login1.answer.value==""){
12       alert('请输入问题验证！');
13       document.login1.answer.focus();
14       return false;
15     }else if(document.login1.answer.value !="199"){
16       alert('问题验证错误！');
17       document.login1.answer.focus();
18       return false;
19     }
20 
21   }
22 </script>

1 <form name="login1" method="post" action=" " onsubmit="return checklogin1();">
2     <div class="regc">            
3             <span class="left">用户名：</span><input class="inputstyle1" type="text" id="username" name="username" />
4             <span class="left">密码：</span><input class="inputstyle1" type="password" id="password" name="password" />
5             <span class="left">问题验证</span><input type="text" name="answer" id="answer" size="20" class="textInt inputstyle1"/>
6             <input type="submit" id="submit" name="submit" value="登录"  class="newFormBtn_red2"/>
7     </div>
8 </form>

去除空格

1  document.login1.username.value.replace(/s/g,'')==''

PHP补充：

1 if(mysql_affected_rows()>0){
2     echo "<script>alert('用户名已存在');window.history.go(-1);</script>";
3     // header("refresh:0;url=./register.php");
4     die;
5 }

window.history.go(-1);也可避免刷新后表单中数据丢失