JavaScript Login function

gistfile1.js

function login() {
  var user = document.getElementById("user_id").value;
  var pass = document.getElementById("pass_id").value;

  var req = new XMLHttpRequest();
  req.open("POST", "http://192.168.1.63:8000/weather/login/", true);
  req.setRequestHeader('Content-Type', 'application/json');
  req.withCredentials = true;
  req.onreadystatechange = function() {
    if (req.readyState == XMLHttpRequest.DONE) {
      if (req.status == 200) {        
        document.getElementById("log_form").style.display = 'none';
        document.getElementById("logged_user").style.display = 'block';
        document.getElementById("logged_user").textContent = document.getElementById("user_id").value;
        document.getElementById("logout_button").style.display = 'block';
        hide_error();
      } 
      else if (req.status == 401) {
        document.getElementById('error_text').textContent = "User/password is incorrect";
        document.getElementById('error').style.display="";
      }
    }
  }
  req.send(JSON.stringify({username: user, password: pass}));
}