tl;dr: fnm is a very fast Node.js version manager, ~40x faster than NVM. It supportsĀ .nvmrc
files and Fish shell out of the box. It works on Linux and Mac and distributed as a single executable - and it is open source on GitHub!
Two weeks ago, I had opened a new tab on my terminal and complained in agony: āOh dear god! Every time I open a new terminal it takes like one second!ā. My teammates looked at me funny. āThis is clearly sub-optimal and hurts my focus, and I believe itās NVMās fault.ā
I found itās NVM that is at fault after I did a search around myĀ .zshrc
file, checking which line takes the most time. It was NVMās initialization. I have been using NVM for years, and I always wanted to write a simple replacement, because my use cases are pretty simple:
nvm install
)nvm use
)These tasks arenāt hard to solve. Node.js binaries are distributed in tarballs on their website, and switching versions shouldnāt be more than just changing a symbolic link around. So, why is NVM so slow?
I thought about writing it as a simple Bash script, just like NVM, but I wanted it to be interesting and fun. Also, not all machines have Bash installed, or there might be problems integrating with Bash. I have used Fish shell for years, and in order to use NVM, I had to use a wrapper that fixes things. It wasnāt easy. Using a real executable, on the other hand, would work on every shell!
My first prototype was a TypeScript app. I packaged it with Zeitās pkg, making it a self-contained executable, because I didnāt want to have dependency on Node. I wanted it to work on a system without Node installed (so the first version of Node would be installed using fnm!)
Nodeās startup time wasnāt good enough for me. Just spawning a āhello worldā takes around 200ms, which is good for servers, and for command line utilities that you donāt use frequently, maybe, but some people use nvm
on every cd
, so their Node version will always be in sync. 200ms penalty for every cd
is madness and would make the tool unusable.
So it seems like I need to write it in a language that is compiled (so no dependencies on the host system), and with a fast boot time. Four languages came to mind: Go, Rust, Crystal and Reason/OCaml.
I chose Reason for many Reasons (hehe), some of them are written in another post. I had used [esy](https://esy.sh/)
and [pesy](https://github.com/jordwalke/pesy)
, two awesome packages that make the development workflow for native Reason/OCaml apps easy-peasy for Node.js developers.
esy
works like a super-powered [yarn](https://yarnpkg.com/)
: it installs packages from npm or OPAM (OCaml package manager) and stores it in a global cache. It also manages a sandbox for the OCaml runtime/dependencies for you, so different OCaml installations wonāt interrupt each other. pesy
generates build configurations for Dune, OCamlās build tool, right from the package.json
file.
When using both packages, it feels just like Node developmentāāāeverything works with a single package.json
file, with minimum configurations. It can also help other Node devs, just like it helped me, to contribute to the project, because Reason syntax is very close to JSā, and the toolchain feels _very_JavaScript-ish.
I had built the first prototype, and tested its performance. I had two test files, one using NVM and one using fnm. Both tests spawned a plain Bash, called the āinitializationā of the target (NVM/fnm), and then switched to the Node version specified inĀ .nvmrc
file in the directory using the target. I ran it 10 times for each binary, and the results were amazing:
So in that test, on my MacBook Pro, fnm was 40 times faster than NVM. Thatās pretty huge, despite not being very scientific.
A real-time animated video is on the repoāsĀ README
When I had started working on fnm, I joined the Reason Discord server, and asked some help from people. I found that community is so nice. When I decided to release, I wrote a short message on the #native-development
channel and immediately got great feedback, telling me itās a great idea.
The community aspect is such an important part of JavaScript, and Reasonās community feels even nicer than JSāāāāmaybe because the community is still small, but it is very welcoming.
I released fnm to GitHub as open source, tweeted about it and went to bed. When I woke up,
Thatās a big deal.
fnm has some features still missing. Here are only a few things we want to add:
tar
and curl
So if you feel like youāre ready to use it and start working faster, or youāre a JS/Reason developer willing to contribute to an open source project, download fnm and join us on GitHub!