Object.create()

gistfile1.js

function Person(name, age) {
	this.name = name;
	this.age = age;
}
Person.prototype.sayHi = function() {
	console.log('Hi')
};
var P1 = Object.create(Person.prototype, {
	name: {
		value: 'P1',
		writable: true,
		enumerable: true
	},
	age: {
		value: 20
	}
});
console.log(P1.name);	//P1
console.log(P1.age);	//20
P1.name = 'abc';
P1.age = '25';
console.log(P1.name);	//abc
console.log(P1.age); 	//20 (can't setting)
var pKeys = Object.keys(P1);
console.log(pKeys);	//[ 'name' ]