piano/js/libs/flight/lib/advice.js

// ==========================================
// Copyright 2013 Twitter, Inc
// Licensed under The MIT License
// http://opensource.org/licenses/MIT
// ==========================================

define(

  [
    './compose'
  ],

  function(compose) {
    'use strict';

    var advice = {

      around: function(base, wrapped) {
        return function composedAround() {
          // unpacking arguments by hand benchmarked faster
          var i = 0, l = arguments.length, args = new Array(l + 1);
          args[0] = base.bind(this);
          for (; i < l; i++) args[i + 1] = arguments[i];

          return wrapped.apply(this, args);
        };
      },

      before: function(base, before) {
        var beforeFn = (typeof before == 'function') ? before : before.obj[before.fnName];
        return function composedBefore() {
          beforeFn.apply(this, arguments);
          return base.apply(this, arguments);
        };
      },

      after: function(base, after) {
        var afterFn = (typeof after == 'function') ? after : after.obj[after.fnName];
        return function composedAfter() {
          var res = (base.unbound || base).apply(this, arguments);
          afterFn.apply(this, arguments);
          return res;
        };
      },

      // a mixin that allows other mixins to augment existing functions by adding additional
      // code before, after or around.
      withAdvice: function() {
        ['before', 'after', 'around'].forEach(function(m) {
          this[m] = function(method, fn) {

            compose.unlockProperty(this, method, function() {
              if (typeof this[method] == 'function') {
                this[method] = advice[m](this[method], fn);
              } else {
                this[method] = fn;
              }

              return this[method];
            });

          };
        }, this);
      }
    };

    return advice;
  }
);