This is a really small example that demonstrates ghcjs/jsaddle#64

To run:

cabal new-run

Then open http://localhost:8085/ in your browser and click the button.

On chrome it works fine. Under firefox it errors with:

Error : Unexpected Duplicate. syncCallbacks=True nBatch=2 nExpected=4

and the app spins sending many requests to jsaddle-warp.