sample.js

function Parent(name){
    this.name = name || 'Adam';
}

Parent.prototype.say = function(){
    return this.name;
}

function Child(name){
    Parent.apply(this, arguments);
}

Child.prototype = new Parent();

var kid = new Child("Patrick");
console.log(kid.name);
console.log(kid.say());
delete kid.name;
console.log(kid.say());