Mixin that doesn't know anything about the object it's mixed into. Check http://disq.us/p/1ba1awd for discussion

mixin.js

var Person = {
    init: function(name) {
        this.name = name;
    },
    doSomethingAndUseSpeak: function(text) {
        this.speak({name: this.name, text})
    }
};

var canSpeak = {  
    speak: function(conf) {console.log(conf.name + ': ' + conf.text)}
};


var bob = Object.assign(Object.create(Person), canSpeak)
bob.init("Bob the Builder")
bob.doSomethingAndUseSpeak('Can we fix it? Yes! We can...')

var jack = Object.assign(Object.create(Person), canSpeak)
jack.init("Jack Sparrow")
jack.doSomethingAndUseSpeak('The seas may be rough, but I am the Captain! No matter how difficult I will always prevail.')