对象原型

function Person() {
}
 
Person.prototype.name="Nicholas";
Person.prototype.age=29;
Person.prototype.sayName=function(){
    alert(this.name);
}
 
var person1=new Person();
person1.name="Greg";
 
var person2=new Person();
 
console.log(person1.hasOwnProperty("name"));//true
console.log(person2.hasOwnProperty("name"));//false
 
console.log("name" in person1);//true
console.log("name" in person2);//true
 
for (var prop in person1) {
    console.log(prop);//name   age   sayName
}
 
function hasPrototypeProperty(object,pro) {//如此可判断存在于原型中的属性
    return (!object.hasOwnProperty(pro))&&(pro in object);
}
console.log(hasPrototypeProperty(person1,"name"));//false
console.log(hasPrototypeProperty(person2,"name"));//true