组合使用构造函数模式和原型模式创建自定义类型

function Person(name, age, job){
  this.name = name;
  this.age = age;
  this.job = job;
  this.friends = ["Shelby", "Court"];
}

Person.prototype = {
  constructor: Person,
  sayName: function(){
    alert(this.name);
  }
}

var person1 = new Person("Nicholas", 29, "Software Engineer");

var person2 = new Person("Greg", 27, "Doctor");

person1.friends.push("Van");

alert(person1.friends);          // "Shelby, Count, Van"

alert(person2.friends);          // "Shelby, Count"

alert(person1.friends === person2.firends);          // false

alert(person1.sayName === person2.sayName);          // true