HTML form submission method case study

<script type="text/javascript">
         function check(form) {
              if(form.userId.value=='') {
                    alert("Please enter your user account!");
                    form.userId.focus();
                    return false;
               }
               if(form.password.value==''){
                    alert("Please enter your login password!");
                    form.password.focus();
                    return false;
                 }
                 return true;
         }
</script>
<form action="login.do?act=login" method="post">
    User Account<input type=text name="userId" size="18" value="" ><br>
    Login password<input type="password" name="password" size="19" value=""/>      
           <input type=submit name="submit1" value="Login" onclick="return check(this.form)">  
</form>

<script type="text/javascript">
         function check(form) {
              if(form.userId.value=='') {
                    alert("Please enter your user account!");
                    form.userId.focus();
                    return false;
               }
               if(form.password.value==''){
                    alert("Please enter your login password!");
                    form.password.focus();
                    return false;
                }
                  document.myform.submit();
            }
    </script>
<form action="login.do?act=login" name="myform" method="post">
    User Account<input type=text name="userId" size="18" value="" ><br>
    Login password<input type="password" name="password" size="19" value=""/>      
    <input type=button name="submit1" value="Login" onclick="check(this.form)">  
</form>

<script type="text/javascript">
         function check(form) {
              if(form.userId.value=='') {
                    alert("Please enter your user account!");
                    form.userId.focus();
                    return false;
               }
               if(form.password.value==''){
                    alert("Please enter your login password!");
                    form.password.focus();
                    return false;
                }
                return true;
         }
</script>
<form action="login.do?act=login" method="post" onsubmit="return check(this)">
    User Account<input type=text name="userId" size="18" value="" ><br>
    Login password<input type="password" name="password" size="19" value=""/>      
    <input type=submit name="submit1" value="Login"> 
</form>