Handy helper function to help battle jQuery addiction. [ES6]

request.js

export function request(options = {}){

  // Usage:
  // request({
  //  url: "example.com",
  //  data: document.querySelector("form"), //FormData-object or form element
  //  method: "POST",
  //  headers: {key: "value"},
  //  success: function(response, status){},
  //  error: function(error, status){},
  //  progress: function(status){}
  // })

  if(!Object.keys(options).length){
    throw Error("Valid arguments required");
  }

  let method = options.method.toUpperCase();
  let url = options.url;
  let data = options.data;
  let headers = options.headers;

  let onload = options.success;
  let onerror = options.error;
  let onprogress = options.progress;

  let request = new XMLHttpRequest();

  request.open(method, url, true);

  for(let key in headers){
    if(!headers.hasOwnProperty(key)){
      continue;
    }
    request.setRequestHeader(key, headers[key]);
  }


  request.onload = function() {
    if (request.status >= 200 && request.status < 400) {
      if(typeof onload === "function"){
        onload(request.responseText, request.statusText);
      }
    }
    else {
      if(typeof onerror === "function"){
        onerror(request.responseText, request.statusText);
      }
    }
  };

  request.onprogress = function(){
    if(typeof onprogress === "function"){
      onprogress(request);
    }
  };

  request.onerror = function(err){
    if(typeof onerror === "function"){
      onerror(err);
    }
  };

  if(data instanceof HTMLElement){
    // Assume we're dealing with a form here. Take the element and "serialize" it.
    data = new FormData(data);
  }

  if(data){
    request.send(data);
  }

  else{
    request.send();
  }

  return request;
}