TypeError:在对象函数Object()中找不到函数项

var obj = new Object();
obj.name = "John";
obj.age = 25;

console.log(obj.name); // 输出 "John"
console.log(obj.age); // 输出 25

var obj = new Object();
obj.sayHello(); // TypeError: obj.sayHello is not a function

var obj = {
  sayHello: function() {
    console.log("Hello!");
  }
};

obj.sayHello(); // 输出 "Hello!"

function Person() {}

Person.prototype.sayHello = function() {
  console.log("Hello!");
};

var obj = new Person();
obj.sayHello(); // 输出 "Hello!"

class Person {
  sayHello() {
    console.log("Hello!");
  }
}

var obj = new Person();
obj.sayHello(); // 输出 "Hello!"