Creating cross browser XHR object

createXHR.js

function createXHR() {
  if (!createXHR.__memoize) {
    var factory = [
      function () {return new XMLHttpRequest()},
      function () {return new ActiveXObject("Microsoft.XMLHTTP")},
      function () {return new ActiveXObject("Msxml3.XMLHTTP")},
      function () {return new ActiveXObject("Msxml2.XMLHTTP")},
    ];
    
    var xhr;
    for (var i=0, l=factory.length; i<l; i++) {
      try { xhr = factory[i](); } catch (e) { continue; }
      createXHR.__memoize = factory[i];
      break;
    }
    return xhr;
  }
  return createXHR.__memoize();
}