Vanilla JS xhttp requst with json

gistfile1.txt

const jsonObject = {
  //key values
}

const xhttp = new XMLHttpRequest();
  xhttp.onreadystatechange = function() {
    if (this.readyState == 4 && this.status == 200) {
      //on complete
    }
  }
  xhttp.open("POST", "/path_to_call", true)
  xhttp.setRequestHeader('Content-Type', 'application/json; charset=UTF-8')
  xhttp.send(JSON.stringify(jsonObject))