js表单提交的三种方式

<script type="text/javascript">  
    function check(form) {  
        if (form.userId.value == ‘‘) {  
            alert("请输入用户帐号!");  
            form.userId.focus();  
            return false;  
        }  
        if (form.password.value == ‘‘) {  
            alert("请输入登录密码!");  
            form.password.focus();  
            return false;  
        }  
        return true;  
    }  
</script>  
  
<form action="login.do?act=login" method="post">  
    用户帐号  
    <input type=text name="userId" size="18" value="">  
    <br>  
    登录密码  
    <input type="password" name="password" size="19" value=""/>  
    <input type=submit name="submit1" value="登陆" onclick="return check(this.form)">  
</form>  

<script type="text/javascript">  
    function check(form) {  
        if (form.userId.value == ‘‘) {  
            alert("请输入用户帐号!");  
            form.userId.focus();  
            return false;  
        }  
        if (form.password.value == ‘‘) {  
            alert("请输入登录密码!");  
            form.password.focus();  
            return false;  
        }  
        return true;  
    }  
</script>  
  
<form action="login.do?act=login" method="post" onsubmit="return check(this)">  
    用户帐号  
    <input type=text name="userId" size="18" value="">  
    <br>  
    登录密码  
    <input type="password" name="password" size="19" value=""/>  
    <input type=submit name="submit1" value="登陆">  
</form> 

<script type="text/javascript">  
    function check(form) {  
        if (form.userId.value == ‘‘) {  
            alert("请输入用户帐号!");  
            form.userId.focus();  
            return false;  
        }  
        if (form.password.value == ‘‘) {  
            alert("请输入登录密码!");  
            form.password.focus();  
            return false;  
        }  
        document.myform.submit();  
    }  
</script>  
  
<form action="login.do?act=login" name="myform" method="post">  
    用户帐号  
    <input type=text name="userId" size="18" value="">  
    <br>  
    登录密码  
    <input type="password" name="password" size="19" value=""/>  
    <input type=button name="submit1" value="登陆" onclick="check(this.form)">  
</form>