in cmd set Visual Studio path depending upon ur version as
Visual Studio 2010 (VS10): SET VS90COMNTOOLS=%VS100COMNTOOLS%
Visual Studio 2012 (VS11): SET VS90COMNTOOLS=%VS110COMNTOOLS%
Visual Studio 2013 (VS12): SET VS90COMNTOOLS=%VS120COMNTOOLS%
Check if python is installed and configured .
Python version <3 is required
then in cmd use command
npm install ffi
to install ffi . For more help look at Cannot install node modules that require compilation on Windows 7 x64/VS2012