function  Property() {
 var xmlhttp;
 if (window.XMLHttpRequest) {
  xmlhttp = new XMLHttpRequest();
 } else {
  xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
 }
    .
 xmlhttp.onreadystatechang e = function() {
  if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
   var datastr = xmlhttp.responseText;
   alert(datastr);
   var dataobj = JSON.parse(datastr)
   let dataarr = [];
   for (let i in dataobj) {
    dataarr.push(dataobj[i]);
   }
   
   
  }
 }
 
 xmlhttp.open("POST", "https://api.123321yun .com/api/device/queryProjectDeviceParamStatus?projId=66", true);

/* xmlhttp.open("POST", "https://api.123321yun.com/api/user/login?username=test123&password= 123456", true);*/ xmlhttp.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
 xmlhttp.send(); 
}

小白求解决登录状态没法保存的问题