Html/ Javascript login

I am in the middle of making a one use login using javascript to create if else statements to see if the input from my html form matches the correct username and login. i haven't been able to find out what the problem is but something is keeping it from loading the link i have it set to open when you use the correct login or even the wrong password text.

KEYNOTE : most of my code is from w3schools

</div> <!-- /container -->
      
      <div align="center" class = "container">
      
         <form class = "form-signin" role = "form" id ="LoginF"
               action ="" method="post"
                           <h4> </h4>
            <input type = "text" class = "form-control" 
               name = "username" id ="username" placeholder = "username = Johnny Appleseed" 
               required autofocus color="#00DD19"><br> 
            &nbsp;<input type = "password" class = "form-control"
               name = "password" id="password" placeholder = "password = Yum @pple$" required>
            <br><button class = "btn btn-lg btn-primary btn-block" type = "submit" 
               name = "login" id = "login" onclick="myFunction()">Login</button>
         <script>
        function myFunction() { 
        String username =
                document.getElementById("username");
        String password =
                document.getElementById("password");
        
                String Cusername = "TeacherLogin";
                String Cpassword = "Hapke";
                String Wrong = "Wrong user name or password";
                if (username = Cusername){
                        
                        if (password = Cpassword){ 
                        window.open("https://mail.google.com/mail/");
                        }else {System.out.print(Wrong);}
                }else{System.out.print(Wrong);}
        }
        
        
        </script>