作用域链

作用域链

  var a = 10;
  function fn(){
  var b = 10
  console.log(b);
  function fun1(){
   console.log（c）;
   b += 6;
   var c = 1;
   function fun2(){
   }
   fun2();
  }
  fun1();
  console.log(b);
}
fn();

然后fun2(),fun1(),fun()依次出栈，活动对象依次消失。