make op available in trigger func
Not against this idea but not sure that this implementation is the best. It would be nice to not have the extra arguments contain a string value. Perhaps 2 boolean arguments: rowExistsNow and isUpdate instead.
Anyways, please include an update to the README.md as well as creating a test case to ensure that the correct arguments are passed. This will probably be accomplished easiest by creating a new JavaScript file and including it in test/index.js.
I recently added something similar to my mysql-live-select package: https://github.com/numtel/mysql-live-select/commit/6e20eaa09e5e0bc2f5cb8a3b52a58e79569e1956
If you don't feel up to all the requirements, I may give it a go but no guarantees as to the timeframe.