наследование

protos.js

var Me = function(){
    this.name = 'Dmitriy';
}

Me.prototype.printName = function(){
    console.log(this.name);
}

var You = function(){
    this.name = 'Username';
}

You.prototype.printName = Me.prototype.printName;

var me = new Me();
var you = new You();

me.printName();
you.printName();

You.prototype.printName = function(){
    console.log('Leonide');
}

you.printName();