抛出两个问题

1.1

function A () {

  }
  A.prototype.n = 1

  var b = new A()

  A.prototype = {
    n: 2,
    m: 3
  }

  var c = new A()
  console.log(b.n, b.m, c.n, c.m)

1.2

function F (){}
  Object.prototype.a = function(){
    console.log('a()')
  }
  Function.prototype.b = function(){
    console.log('b()')
  }
  
  var f = new F()
  f.a()
  // f.b()
  F.a()
  F.b()
  console.log(f)
  console.log(Object.prototype)
  console.log(Function.prototype)

2.1

A.prototype = {
    n: 2,
    m: 3
  } //A的显示原型指向了这个对象，而不是一个空的Object了

//1 undefined 2 3

2.2

JS进阶 九——面试题_练习题