Yes you're right. 49mb is slightly large for REPL. but I've been working successfully with 200k lines CSV of over 15mb without issue
All it does is JSON.parse, execute your series of functions then JSON.stringify.
Unless I'm missing something there is no advantage over ad-hoc javascript. If you want to load a file from disk, deserialize and do some processing in javascript then node is absolutely the right tool (and this isn't).