I have been trying to get an answer to this without really finding any. Excuse me if this sounds stupid or obvious. 

I have a nodejs application and basically I would like to simply get the resolution of a video. Imagine I have film stored on disk and I would like to be able to know if it is in 720p or 1080p or anything else. 

I understood that I might need to use ffmpeg to do so, but then I also understood that ffmpeg was mostly used to "record, convert and stream audio and video files".
That does not mean retrieve video resolution. 

Thank you for your help

Edit 1:
The node.js app is a desktop app and needs to be portable to Linux, windows and OS X. If possible a portable answer would be more appreciated but of course any answer is welcome.