AJAX(async JacaScript and XML(JSON))

const ajax = (method, url, data, success, fail) => {
  var request = new XMLHttpRequest()
  request.open(method, url)
  request.onreadystatechange = function() {
    if(request.readyState === 4){
      if(request.status >= 200 && request.status < 300 ||request.status ===304){
      success(request)
      }else{
        fail(request)
        }
    }
  };
  request.send
}