-----------------------------------------------------------------
cc = function(){alert(345)},
pushStack = function() {
    cc();
},
pushStack();//345

//没加var的放在window对象中
pushStack = function() {
    cc();
},
cc = function(){alert(345)},
pushStack();//345
----------------------------------------------------------------
pushStack = function() {
    cc();//cc is not defined
};
pushStack();
cc = function(){alert(345)};


pushStack = function() {
    cc();
};
pushStack();//345
function cc(){alert(345)};
----------------------------------------------------------------
cc = function(){alert(345)};
pushStack();//pushStack is not defined ,js解析器执行到这里的时候pushStack还是未定义
pushStack = function() {
    cc(); 
};

cc = function(){alert(345)};
pushStack();//345,js解析器执行到这里的时候pushStack已经定义了
function pushStack() {
    cc(); 
};

name = ‘2‘;
a = function(){
    alert(this.name);
    alert(888);
},
o =　{
    fn1 : function(){
            a = function(){ 
            //fn1执行的时候（fn1要执行，不执行是加不进去的）把a加到window里面去，把外部的a方法覆盖了
                alert(this.name);//2  window
                alert(this);//2
                alert(666);
            };
            a();//666  a.call(window)
            window.a();//666
    }
}
o.fn1();
window.a();// 2   666

name = ‘2‘;
a = function(){
    alert(this.name);
    alert(888);
},
o =　{
    fn1 : function(){
            this.a = function(){//fn1执行，给o对象加了a方法
                alert(this.name); 
                alert(this);
                alert(666);
            };
            a(); //2   888    a.call(window)   ，都是从window中找a()没有就报错
            window.a(); //2  888
    }
}
o.fn1();
window.a();// 2   888
o.a();//666

name = ‘2‘;
a = function(){
    alert(this.name);
    alert(888);
},
o =　{
    fn1 : function(){
            var a = function(){ //fn1函数执行，就有2个a方法，一个在fn1局部作用域，一个在window
                alert(this.name); 
                alert(this);
                alert(666);
            };
            a(); //2  666  a.call(window)，查找局部作用域的a方法
            window.a(); // 2  888
    }
}
o.fn1();
window.a();//  2   888