split batch from channel reader

I have a CSV file input that worked well when I do a custom 'split batch by javascript', but we want to handle many different types of files while using the same input directory. I created a channel that based on the filename,will pick up the file and routeMessage to the appropriate channel. All well and good, but now I can not run the custom code that was splitting my batches. Any ideas how to do this?



Basically since the 2nd channel is no longer using a file reader, I do not have access to the Split Message By Javascript. Is this something I can stick in the pre-processor?

split batch from channel reader