Good way to do OOP in JS

OOP.js

var MyProject = {};

var newobj = function (args) {
    return {
        public: {},
        private: args || {}
    };
};

var extendsfrom = function (classname, args) {
    return {
        public: classname(args),
        private: args || {},
        base: Object.assign({}, args)
    };
}

MyProject.classA = function (args) {
    var self = newobj(args);
    var public = self.public;
    var private = self.private;
    
    public.say_quote = function () {
        private.say_name(private.quote);
    };
    
    private.say_name = function (str) {
        private.say(private.name + " says: " + str);
    };
    
    private.say = function (str) {
        document.writeln(str);
    };
    
    return public;
};

MyProject.classB = function (args) {
    var self = extendsfrom(MyProject.classA, args);
    var public = self.public;
    var private = self.private;
    var base = self.base;
    
    public.say_quote = function () {
        private.say_name(private.quote + '!');
    };
    
    private.say_name = function (str) {
        private.say(private.name + " thinks: " + str);
    };
    
    private.say = function (str) {
        base.say(str);
        base.say("also hi");
    };
    
    return public;
};

var a1 = MyProject.classA({name: "bill", quote: "eee"});
a1.say_quote();

var a2 = MyProject.classA({name: "abe", quote: "aaaaa"});
a2.say_quote();

var a3 = MyProject.classB({name: "harkinian", quote: "hmm"});
a3.say_quote();
a2.say_quote();
a1.say_quote();