Minimalist AJAX function for the most basic calls. Only supports GET method. Loads given url and sends result to the callback function. Callback attribute is optional, sometimes you just want to ping the server and you don't care about the response.

ajax.js

function ajax (url, callback) {
  callback = callback || function () {};
  var xhr = new XMLHttpRequest();
  xhr.onreadystatechange = function () {
    if (xhr.readyState == 4) {
      callback(xhr.responseText);
    }
  };
  xhr.open("GET", url, true);
  xhr.send();
}

Many thanks! Simple and short.