sample advice extension. forgot the origins of this...

advice.js

(function (exports) {
  //usage
  //withAdvice.call(targetObject);

  //mixin augments target object with around, before and after methods
  //method is the base method, advice is the augmenting function
  exports.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 = Array.prototype.slice.call(arguments, 0);
        return wrapped.apply(this, [base.bind(this)].concat(args));
      }
    },
    before: function(base, before) {
      return fn.around(base, function() {
        var args = Array.prototype.slice.call(arguments, 0),
            orig = args.shift();
  
        before.apply(this, args);
        return (orig).apply(this, args);
      });
    },
    after: function(base, after) {
      return fn.around(base, function() {
        var args = Array.prototype.slice.call(arguments, 0),
            orig = args.shift(),
            res = orig.apply(this, args);

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

}(typeof exports === 'undefined' ? this.advice = {} : exports));