Create XHR function

createXHR.js

// Function for creating an XHR object which is compatible in all browsers.
// This implementation is compatible with the original Internet Explorer version.
// So, it can be used to create an XHR object in any browser.
// Example usage:
// var xhr = createXHR();
// xhr.onreadystatechange = function() {
//  if(xhr.readyState == 4) {
//    if((xhr.status >= 200 && xhr.status < 300) || xhr.status == 304) {
//      alert(xhr.responseText);
//    } else {
//      alert("Request was unsuccessful: " + xhr.status);
//    }
//  }
// };
// xhr.open("GET", "data.json", true);
// xhr.send(null);

function createXHR() {
  if (typeof XMLHttpRequest != "undefined") {
    return new XMLHttpRequest();
  } else if (typeof ActiveXObject != "undefined") {
    if (typeof arguments.callee.AtiveXString != "string") {
      var versions = ["MSXML2.XMLHttp.6.0", "MSXML2.XMLHttp.3.0", "MSXML2.Http"],
          i,
          len;
      
      for(i = 0, len = versions.length; i < len; i++) {
        try {
          new ActiveXObject(versions[i]);
          arguments.callee.ActiveXString = versions[i];
          break;
        }
        catch(ex) {
          // skip
        }
      }
    }
  } else {
    throw new Error("No XHR object available.");
  }
}