html界面如何用javascript分别验证两个不同的表单？

不知道为什么，同一个界面两个表单两个函数，但是就是只执行注册部分的表单验证后跳转，登录部分还是不验证直接跳转……
HTML表单相关代码

    <div class="form-box">
        <!--注册设计-->
        <form class="register-box hidden" action="./zcjm.php" method="post">
            <h2>注册新的账号</h2>
            <div class="form-control">
                <input type="text" id="Username" class="qkk" name="Username" placeholder="用户名" autocomplete="off">
                <lable class="error-message"></lable>
            </div>
            <div class="form-control">
                <input type="text" id="Phone" class="qkk" name="Phone" placeholder="手机号码" autocomplete="off">
                <lable class="error-message"></lable>
            </div>
            <div class="form-control">
                <input type="password" id="Password" class="qkk" name="Password" placeholder="密码" autocomplete="off">
                <lable class="error-message"></lable>
            </div>
            <div class="form-control">
                <input type="password" id="Confirm" class="qkk" placeholder="确认密码" autocomplete="off">
                <lable class="error-message"></lable>
            </div>
            <input type="submit" class="btn" value="注册" onclick="return check()">
        </form>
        <!--登录设计-->
        <form class="login-box" action="./dljm.php" method="post">
            <h2>登录已有账号</h2>
            <div class="form-control">
                <input type="text" id="Usernamelog" class="qkk" placeholder="用户名" autocomplete="off" onblur="checkuser()">
                <lable class="error-message"></lable>
             </div>
            <div class="form-control">
                <input type="password" id="Passwordlog" class="qkk" placeholder="密码" autocomplete="off" onblur="checkpwd()">
               <lable class="error-message"></lable>
             </div>
            <a href="#">忘记密码?</a>
            <input type="submit" class="btn" value="登录">
        </form>
</div>

JS相关代码
const Username = document.getElementById('Username');
const Phone = document.getElementById('Phone');
const Password = document.getElementById('Password');
const Confirm = document.getElementById('Confirm');
const Usernamelog = getElementById('Usernamelog');
const Passwordlog = getElementById('Passwordlog');

    function check()
    {
        const UsernameValue = Username.value.trim();
        const PhoneValue = Phone.value.trim();
        const PasswordValue = Password.value.trim();
        const ConfirmValue = Confirm.value.trim();
        
        if(UsernameValue=="")
        {
            printError(Username,"用户名不可为空！");
            return false;
        }
        else if(!validateUsername(UsernameValue))
        {
            printError(Username,"用户名不可少于4个字符！");
            return false;
        }
        else
        {
            removeError(Username);
        }
        
        if(PhoneValue=="")
        {
            printError(Phone,"手机号码不可为空！");
            return false;
        }
        else if(!validatePhone(PhoneValue))
        {
            printError(Phone,"手机号码无效");
            return false;
        }
        else
        {
            removeError(Phone);
        }
        
        if(PasswordValue=="")
        {
            printError(Password,"密码不可为空！");
            return false;
        }
        else if(!validatePassword(PasswordValue))
        {
            printError(Password,"密码必须由6-16位字母和数字组成！");
            return false;
        }
        else
        {
            removeError(Password);
        }
        
        if(ConfirmValue=="")
        {
            printError(Confirm,"请再次输入以确认密码");
            return false;
        }
        else if(PasswordValue !== ConfirmValue)
        {
            printError(Confirm, "两次密码不一致");
            return false;
        } 
        else
        {
            removeError(Confirm);
        }
    }

    function check2()
    {
        const UsernamelogValue=Usernamelog.value.trim();
        const PasswordlogValue=Passwordlog.value.trim();
        if(UsernamelogValue=="")
            {
                printError(Usernamelog,"用户名不可为空！");
                return false;
            }
        else
            {
                removeError(Usernamelog);
            }
        if(PasswordlogValue=="")
            {
                printError(Passwordlog,"密码不可为空！");
                return false;
            }
        else
            {
                removeError(Passwordlog);
            }
    }
    
    function printError(input,message)
    {
        const formContorl=input.parentElement;
        formContorl.classList.add('error');
        formContorl.querySelector('.error-message').textContent=message;
    }
    function removeError(input)
    {
        const formContorl=input.parentElement;
        formContorl.classList.remove('error');
        formContorl.querySelector('.error-message').textContent="";
    }
    function validateUsername(Username)
    {
        const Username_reg = /.{4,}/;
        return Username_reg.test(Username);
    }
    function validatePhone(Phone)
    {
        const Phone_reg = /^((1[3,5,8][0-9])|(14[5,7])|(17[0,6,7,8])|(19[7]))\d{8}$/;
        return Phone_reg.test(Phone);
    }
    function validatePassword(Password)
    {
        const Password_reg = /^(?![0-9]+$)(?![a-zA-Z]+$)[0-9A-Za-z]{6,16}$/;
        return Password_reg.test(Password);
    }

运行结果就是——只有注册的表单可以验证后跳转，登录的表单还是直接跳转并且在数据库中存储空值……
查了好多多表单单独验证的方法，但是都没有用……也不会ajax和vue，想请问只用js可不可以实现单独验证呢？非常感谢！

通过获取本地数据，然后遍历，登录输入不同账户密码进行匹配，有就跳转