var AAA = function(name, age) {

	this.name = name ;

	this.age = age;

}

AAA.prototype.getName = function() {

	console.log(this.name);

}

AAA.prototype.getAge = function() {

	console.log(this.age);

}

var BBB = function(name, age, comments) {

	if(this instanceof BBB) {

		AAA.call(this, name, age);

		this.comments = comments;

	} else{

		return new BBB(name, age, comments);

	}

};

BBB.prototype = new AAA();

BBB.prototype.getComments = function() {

	console.log(this.comments);

}

var bbb = BBB('mhp', 17, 'b');

console.dir(bbb);

bbb.getName();

bbb.getAge();// 17

bbb.getComments();// b

console.log(BBB.prototype instanceof AAA);