It depends on what you need. If you are happy with chrome/chromium's developer tools (for example for memory monitoring) you can use them with nw.js too.
Here's a little explanation on how to get them:
https://github.com/nwjs/nw.js/wiki/debu ... h-devtools
If you are looking for something like the Unity profiler for in-depth rendering analysis, I don't have an answer.