Convert Raw to Wav Streams in NodeJS
The addon is a wrapper around a C++ library called portaudio which according to its documentation supports writing to a WAV file.
What you could do is extend the addon and bind a NodeJS function to the underlying C++ function that write to WAV.This will give you a good performance if it is an issue.
If you want something easier you could look up utilities that do the conversion and call them from within your script using ex like this