AJAX in 14 lines of JavaScript

ajax.js

function ajax(url, callback, data, x) {
  try {
    x = new(this.XMLHttpRequest || ActiveXObject)('MSXML2.XMLHTTP.3.0')
    x.open(data ? 'POST' : 'GET', url, 1)
    x.setRequestHeader('X-Requested-With', 'XMLHttpRequest')
    x.setRequestHeader('Content-type', 'application/json')
    x.onreadystatechange = function () {
      x.readyState > 3 && callback && callback(x.responseText, x)
    }
    x.send(JSON.stringify(data))
  } catch (e) {
    window.console && console.log(e)
  }
}