gistfile1.js

var B = {
  foo: function (original) {
    console.log("Foo B");
    original();
  }.enhance()
};

var C = {
  foo: function () {
    console.log("Foo C");
  }
};


var A = SC.Object.extend(C, B, {
  foo: function (original) {
    console.log("Foo A");
    original();
  }.enhance()
});

A.create().foo();