prototype.js

function Person() {
    //public member
    this.Name = "Copenhaver";

    //convention based "private"
    this._ccn = "5555555555555";

    /* thought this was unusable, but it's actually scoped inside 
     * this invocation of the function and usable by other members of
     * the object currently being built.
    var ssn = "xxxxxxxxx";
}

/* this is actually creating a completely separate object that 
 * will act as the parent of all objects built using Person()
Person.prototype = {
    getSSN: function(){
        //this doesn't do what you want
        //actually would try to grab this out of global scope
        return ssn;
    },

    getCCN: function(){
        //anyone could access this variable
        return this._ccn;
    }
};