8、阿里面试函数题

function Foo(){
  Foo.a = function(){
    console.log(1)
  }
  this.a = function(){
    console.log(2)
  }
}
Foo.prototype.a = function(){
  console.log(3)
}
Foo.a = function(){
  console.log(4)
}
Foo.a()                                            //4
let obj = new Foo();        
obj.a()                                            //2 私有属性中有a
Foo.a()                                            //1