Lazy loading function

lazy_loading.js

/**
 * <Professional Javascript for web developer v3 p736>
 * Reduce determine condition in every function execution.
 */
 
// bad ass
function createXHR(){
  if (typeof XMLHttpRequest != “undefined”){
    return new XMLHttpRequest();
  } else if (typeof ActiveXObject != “undefined”) {
    if (typeof arguments.callee.activeXString != “string”){
      var versions = [“MSXML2.XMLHttp.6.0”, “MSXML2.XMLHttp.3.0”,
      “MSXML2.XMLHttp”], 
      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
        }
      }
    }
    return new ActiveXObject(arguments.callee.activeXString);
  } else {
    throw new Error(”No XHR object available.”);
  }
}

// lazy loading
function createXHR(){
  if (typeof XMLHttpRequest != “undefined”){
    createXHR = function(){
      return new XMLHttpRequest();
    };
  } else if (typeof ActiveXObject != “undefined”){
    createXHR = function(){ 
      if (typeof arguments.callee.activeXString != “string”){
        var versions = [“MSXML2.XMLHttp.6.0”, “MSXML2.XMLHttp.3.0”,
          “MSXML2.XMLHttp”],
          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
            }
          }
      }
      return new ActiveXObject(arguments.callee.activeXString);
    };
  } else {
    createXHR = function(){
      throw new Error(“No XHR object available.”);
    };
  }
  return createXHR();
}