Native addons broken
All native addons using NAN version < 2.x are broken. There is a meta-issue on this on the Node.js GitHub repo. Addons using NAN pre 2.x version were already broken on io.js version 3 too but the version 3 did not become widely used before the merge. I maintain the fast-feed feed parser package which uses native code as it binds to a C++ library. Lots of changes had to be made although all of them were trivial. These included changing things like:
Nan::Set(extension, Nan::New("name").ToLocalChecked(), Nan::New<String>(name).ToLocalChecked())
The full changeset is available here.
Travis and old GCC
The merge should agitate people to use more ES6 as Node.js has now much better support for ES6 features. It would be nice if more packages (and the Node.js library) supported promises. Promises are natively available in the version 4 but the
fs module is not using them yet. There also seems to be no
promisify function built-in. Returning promises from the
fs module has been proposed couple of times in the issue tracker but it has not found much support yet.
Built-in NAN/native abstraction?
V8 API has not proved to be very stable between releases and that causes issues for native addons. As one of the solutions, building in NAN has been proposed. However, this is still an open issue.