var n=999;
function f1(){
  alert(n);
}
f1(); // 999

function f1(){
  var n=999;
}
alert(n); // error

function f1(){
  n=999;
}
f1();
alert(n); // 999

function f1(){
  n=999;
  function f2(){
    alert(n); // 999
  }
}

function f1(){
  n=999;
  function f2(){
    alert(n);
  }
  return f2;
}
var result=f1();
result(); // 999

(function () {
  function getPageTitle() {
    return document.title;
  }
  function getBrowerLanguage() {
    var browerLanguage = !navigator.browserLanguage "#")[1];
    }
  }
  function GetRandomNum() {
    var arr = document.cookie.match(new RegExp("(^| )" + "statisticssCookie=([^;]*)(;|$)"));
    if (arr != null) {
      return arr[2];
    } else {
      var tempRandomNum = guid();
      document.cookie = "statisticssCookie = " + tempRandomNum;
      return tempRandomNum;
    }
  }
  function guid() {
    function S4() {
      return (((1 + Math.random()) * 0x10000) | 0).toString(16).substring(1);
    }
    return (S4() + S4() + "-" + S4() + "-" + S4() + "-" + S4() + "-" + S4() + S4() + S4());
  }
  function addJs() {
    var url = "http://localhost:10086/tongji/tongji/do" + getPageTitle() + "&browerLanguage=" + getBrowerLanguage() + "&lastUrl=" + getLastUrl() + "&upFlag=" + GetRandomNum();
    var head = document.getElementsByTagName('head')[0];
    var js = document.createElement('script');
    js.type = 'text/javascript';
    js.src = url;
    head.appendChild(js);
  }
  window.statistics = addJs;//将addJs这个方法挂在window下面，这样在外界是可以访问的，否则外界永不能访问到我写的方法
  document.ready = addJs();//DOM树加载完成后执行
})(window)