javascript中in和hasOwnProperty区别

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

var person1 = new Person();
var person2 = new Person();

alert(person1.hasOwnProperty("name"));//false
alert("name" in person1);//true

person1.name = "Greg";
alert(person1.name);//"Greg"
alert(person1.hasOwnProperty("name"));//true
alert("name" in person1);//true

delete person1.name;
alert(person1.name);//"Nicholas"
alert(person1.hasOwnProperty("name"));//false
alert("name" in person1);//true