an advice functional mixin

advice.js

//usage
withAdvice.call(targetObject);

//mixin augments target object with around, before and after methods
//method is the base method, advice is the augmenting function
withAdvice: function() {
  ['before', 'after', 'around'].forEach(function(m) {
    this[m] = function(method, advice) {
      if (typeof this[method] == 'function') {
        return this[method] = fn[m](this[method], advice);
      } else {
        return this[method] = advice;
      }
    };
  }, this);
}

//fn is a supporting object that implements around, before and after
var fn = {
  around: function(base, wrapped) {
    return function() {
      var args = util.toArray(arguments);
      return wrapped.apply(this, [base.bind(this)].concat(args));
    }
  },
  before: function(base, before) {
    return fn.around(base, function() {
      var args = util.toArray(arguments),
          orig = args.shift();

      before.apply(this, args);
      return (orig).apply(this, args);
    });
  },
  after: function(base, after) {
    return fn.around(base, function() {
      var args = util.toArray(arguments),
          orig = args.shift(),
          res = orig.apply(this, args);

      after.apply(this, args);
      return res;
    });
  }
}