Reconstruct XHR POST request

//boilerplate code for an AJAX POST request using an XMLHttpRequest object.
const xhr = new XMLHttpRequest();

const url = 'https://api-to-call.com/endpoint';
const data = JSON.stringify({id: '200'});  //JSON.stringify() will convert a value to a JSON string. By converting the value to a string, we can then send the data to a server.

xhr.responseType = 'json';

xhr.onreadystatechange = () => {
  if (xhr.readyState === XMLHttpRequest.DONE){
    return xhr.response;
  }
}

xhr.open('POST', url);
xhr.send(data);