call api post and return result

let r = await fetch('/endoint', { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ foo: 'bar' }) })
let data = await r.json()

function getXmlHttp(){
  var xmlhttp;
  try {
    xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
  } catch (e) {
    try {
      xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
    } catch (E) {
      xmlhttp = false;
    }
  }
  if (!xmlhttp && typeof XMLHttpRequest!='undefined') {
    xmlhttp = new XMLHttpRequest();
  }
  return xmlhttp;
}
function openScript(name){
 var xmlhttp=getXmlHttp();
 xmlhttp.open('POST',name,true);
 xmlhttp.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
 return xmlhttp;
}
function renderResponse(xmlhttp) {
 if (xmlhttp.readyState == 4) {
  if(xmlhttp.status == 200) {
   alert(xmlhttp.responseText);
  } else {
   alert('Pierdut!');
  }
 }
}


 var xmlhttp=openScript(link);
 xmlhttp.send('{ foo: \'bar\' }');
 xmlhttp.onreadystatechange=function() {renderResponse(xmlhttp);};