Javascript Ajax移除方法

I am studying basic html, and now working on basic login/logout/create user/delete user (only when logged in as admin) stuff.

I have used PUT to update user password, POST to create user account, and DELETE to logout.

Now I want to delete user account when logged in as admin, but I have no idea how.

This is my third time asking this question here and I know my question is terrible. Hopefully my code will help you understand.

button.addEventListener("click",login);
    function login(){
        if(checkInput(username)==false||checkInput(password)==false){
            alert("bad input");
            return;
        }
        var params= "Name="+username.value+"&"+"password="+password.value;  
        var ajax = new XMLHttpRequest();
        ajax.responseType = "json";
        ajax.addEventListener("load",function(){
            console.log(this.response);

            messageSpan.innerHTML=this.response[0].message;

            if(this.response[0].status==true){
                button.style.display="none";

                logoutButton.style.display="inline";
                createButton.style.display="none";
                updateButton.style.display="inline"
            }

            if(username.value=="admin"){
                deleteButton.style.display="inline";
            }

        });

        ajax.open("POST","//cse.taylor.edu/~cos143/sessions.php");
        ajax.setRequestHeader("Content-type",
        "application/x-www-form-urlencoded");
        ajax.send(params);
    }


logoutButton.addEventListener("click",logout)
    function logout(){
        var ajax = new XMLHttpRequest();
        ajax.responseType = "json";
        ajax.addEventListener("load",function(){
            console.log(this.response[0]);

            messageSpan.innerHTML=this.response[0].message;
            if(this.response[0].status==true){
                button.style.display="inline";
                logoutButton.style.display="none";
                updateButton.style.display="none"
                createButton.style.display="inline";

            }

            deleteButton.style.display="none";

        });
        ajax.open("DELETE","//cse.taylor.edu/~cos143/sessions.php");
        ajax.send();    
    }

so these two are my eventlistener for login button and logout button. You will notice only ajax.open("~~~ has changed. I am going to do the same thing for delete user button, but I have no idea what I should write there!

I have tried remove, but console says unacceptable request type! plz help!

The problem may be on the server side. The server specifies which request types it will accept, and it sounds like maybe DELETE has not been set as one of those allowed types on your server.