text: var a = function func(){
  
  };
  a.stu = {
      name: 'cheng',
      age: 12
  };
  a.arr = [1,2,3];
  a.func = function (){
  
  };
  
  Object.defineProperty(a, 'len', {
      enumerable: true,
      get: function(){
         return this.arr.length;
      }
  });
  console.log(a.len);
  console.log(Object.getOwnPropertyNames(a));
  
  
  
  
  
  
  
  
  
  
  //console.log(Object.getOwnPropertyDescriptor();