I added an xor method to the buffer class that make sure that argument instanceof Buffer. The require('crypto') has a method of randomBytes that gives an object that appears to be a slow buffer.

I am trying to allow xor method of Buffer to only allow Buffer objects and SlowBuffers, but key instanceof SlowBuffer gives an error. Does anyone know how I can detect if key is an instanceof SlowBuffer?

var key;
crypto.randomBytes(10,function(err,bytes) {
  key = bytes;
});
//key instanceof SlowBuffer

The http://nodejs.org/api/buffer.html#buffer_class_method_buffer_isbuffer_obj Buffer.isBuffer method will return true for SlowBuffer and Buffer objects.