Mixins for JavaScript

mixins.js

Function.prototype.mixin = function() {
  for (var i = 0; i < arguments.length; i++) {
    mixin = arguments[i];
    for (p in mixin) {
      this.prototype[p] = mixin[p];
    }
  }
};

var Obj = function() {
};

Obj.mixin({
  foo: function() {
    console.log('bar');
  }
});

var o = new Obj();
o.foo();