code: function(a, b) {
         if (typeof a != typeof b) return
         if (a === b) return true
         if (a instanceof RegExp)
           return a.toString() === b.toString()
         if (a instanceof Date)
           return Number(a) === Number(b)
         if (typeof a != 'object') return
         if (a.length !== undefined)
           if (a.length !== b.length) return
           else
             for (var i = 0, len = a.length; i < len; ++i)
               if (!equal(a[i], b[i]))
                 return
         for (var key in a)
           if (!equal(a[key], b[key]))
             return
         return true
       }
docs: Check if object _a_, is equal to object _b_.
  
  @param  {object} a
  @param  {object} b
  @return {bool}
  @api private