请问为啥同样的代码,左侧请求不带cookie?

   btn3.onclick=()=>$.ajax({

                    type : "get",

                    url: "http://server.com/getCookie",

                    xhrFields:{

                        withCredentials:true

                    },

                    crossDomain: true,

                    success: function(json){

                        result = json;

                    }

                });