vanilla ajax get (with promise)

ajaxGet,js

function ajaxGet(url) {
  return new Promise(function(resolve, reject) {
    let req = new XMLHttpRequest();
    req.open("GET", url);
    req.onload = function() {
      if (req.status === 200) {
        resolve(req.response);
      } else {
        reject(new Error(req.statusText));
      }
    };

    req.onerror = function() {
      reject(new Error("Network error"));
    };
    req.send();
  });
}