code: function map(obj, cb, ctx)
  {
      var result = {};
      forEach(obj, function(key, val){
          result[key] = cb.call(ctx, key, val);
      }, ctx);
      return result;
  }
docs: Standard map over objects
  @param {Object} obj
  @param {Function} cb
  @param {Object} ctx
  @return {Object}