分析javascript原型及原型链

function Person(){
}
Person.prototype.name = "Nicholas";
Person.prototype.age = 29;
Person.prototype.sayName = function(){
alert(this.name);
};
var person1 = new Person();
person1.sayName(); //"Nicholas"
var person2 = new Person();
person2.sayName(); //"Nicholas"
alert(person1.sayName == person2.sayName); //true

用isPrototypeOf()方法判断实例与原型对象之间的关系
alert(Person.prototype.isPrototypeOf(person1)); //true
alert(Person.prototype.isPrototypeOf(person2)); //true

用Object.getPrototypeOf() 方法返回实例的原型对象
alert(Object.getPrototypeOf(person1) == Person.prototype); //true

使用 hasOwnProperty() 方法可以检测一个属性是存在于实例中，还是存在于原型中。
alert(person1.hasOwnProperty("name")); //false　　来着原型
person1.name = "Greg";
alert(person1.name); //"Greg"——来自实例
alert(person1.hasOwnProperty("name")); //true

function Person(){
}
Person.prototype = {
　　name : "Nicholas",
　　age : 29,
　　job: "Software Engineer",
　　sayName : function () {
　　　　alert(this.name);
　　}
};

var friend = new Person();
alert(friend instanceof Object); //true
alert(friend instanceof Person); //true
alert(friend.constructor == Person); //false
alert(friend.constructor == Object); //true

function Person(){
}
Person.prototype = {
  constructor : Person,
  name : "Nicholas",
  age : 29,
  job: "Software Engineer",
  sayName : function () {
    alert(this.name);
  }
};  

function Person(){
}
Person.prototype = {
constructor: Person,
name : "Nicholas",
age : 29,
job : "Software Engineer",
friends : ["Shelby", "Court"],
sayName : function () {
alert(this.name);
}
};
var person1 = new Person();
var person2 = new Person();
person1.friends.push("Van");
alert(person1.friends); //"Shelby,Court,Van"
alert(person2.friends); //"Shelby,Court,Van"
alert(person1.friends === person2.friends); //true

function SuperType(){
　　this.property = true;
}
SuperType.prototype.getSuperValue = function(){
　　return this.property;
};
function SubType(){
　　this.subproperty = false;
}
//继承了 SuperType
SubType.prototype = new SuperType();
SubType.prototype.getSubValue = function (){
　　return this.subproperty;
};
var instance = new SubType();
alert(instance.getSuperValue()); //true