第一種：

復(fù)制代碼 代碼如下:

<script type="text/javascript">
         function check(form) {

          if(form.userId.value=='') {
                alert("請(qǐng)輸入用戶(hù)帳號(hào)!");
                form.userId.focus();
                return false;
           }
       if(form.password.value==''){
                alert("請(qǐng)輸入登錄密碼!");
                form.password.focus();
                return false;
         }
         return true;
         }
</script>

<form action="login.do?act=login" method="post">
用戶(hù)帳號(hào)
  <input type=text size="18" value="" >
<br>
 登錄密碼     
<input type="password" size="19" value=""/>     
 <input type=submit value="登陸"> 

</form>  
 

復(fù)制代碼 代碼如下:

<script type="text/javascript">
         function check(form) {

          if(form.userId.value=='') {
                alert("請(qǐng)輸入用戶(hù)帳號(hào)!");
                form.userId.focus();
                return false;
           }
       if(form.password.value==''){
                alert("請(qǐng)輸入登錄密碼!");
                form.password.focus();
                return false;
         }
         return true;
         }
</script>

<form action="login.do?act=login" method="post" onsubmit="return check(this)">
用戶(hù)帳號(hào)
  <input type=text size="18" value="" >
<br>
 登錄密碼     
<input type="password" size="19" value=""/>     
 <input type=submit value="登陸"> 

</form> 

復(fù)制代碼 代碼如下:

<script type="text/javascript">
         function check(form) {

          if(form.userId.value=='') {
                alert("請(qǐng)輸入用戶(hù)帳號(hào)!");
                form.userId.focus();
                return false;
           }
       if(form.password.value==''){
                alert("請(qǐng)輸入登錄密碼!");
                form.password.focus();
                return false;
         }

          document.myform.submit();
}
</script>

<form action="login.do?act=login" method="post">
用戶(hù)帳號(hào)
  <input type=text size="18" value="" >
<br>
 登錄密碼     
<input type="password" size="19" value=""/>     
<input type=button value="登陸"> 

</form>