The prefilter function often passes an empty path. This param should include the entire path of where the key param exists in the JSON tree. The current empty or one level path is not enough info to make a decision on whether to filter the diff.
I agree with your comment -- that is the intention of the path param so it seems there is a bug. I'll pull it down and add some tests/investigate.
@ravishivt do you find this happening when you are comparing arrays containing objects or objects with properties that are arrays containing objects?
I've got an update that I'm testing right now; it was indeed the path related to arrays. The fix will be a breaking change to the structure of changes. Any change below an array did not report paths correctly to the prefilter (was always null). More info in the check-in readme when it is ready (final).
fix #17, fix #19, close #21