ajax request for loading bar

ajax.js

$.ajax({
    xhr: function()
    {
      var xhr = new window.XMLHttpRequest();
      //Download progress
      xhr.addEventListener("progress", function(evt){
        var percentComplete = evt.loaded / evt.total;
        //Do something with download progress
        console.log("down", percentComplete);
        $('progress').attr("value", percentComplete * 100)
      }, false);
      return xhr;
    },
    url: "/staff",
    success: function(data){
      console.log(arguments);
      $('.staff').html(data);
    }
  });