> What I still don't fully understand is why people want to write non-webpage software in JavaScript, a language designed to run in web pages. Why not Python or

> What I still don't fully understand is why people want to write non-webpage software in JavaScript, a language designed to run in web pages. Why not Python or Go or Rust or literally anything else? I would say familiarity is a big one. Lots of people now learn JavaScript first, and once you know it well, having to re-learn a whole other language might seem like a big hurdle that if you can avoid seems like a good proposition. Another one is this new concept of "full stack". While most JS code in browser and in server won't work as is, there's still a lot of overlap. So you can have subsets of code that you can copy/paste from your front-end into your backend and vice versa. This also means that as a dev, if you want to do backend and frontend work, you only need to learn one language, that's 50% less effort on your part than having to learn two languages :p Something else that kind of happened as a lucky accident is that JavaScript was designed for event driven programming mostly, due to it being used as a language to handle user events on webpages for interactivity. Now it turns out that the problem of managing interactive user interfaces is highly concurrent in nature. At the same time, it happened that most backend code needed to scale horizontally, which meant that it too needed to become highly concurrent. This was the innovation brought by NodeJS to the backend. It was one of the first run-time for backend that was designed exclusively in an event driven model, which actually allowed it to scale quite well for non CPU intensive workloads. In that sense NodeJS was a pioneer on the back end side as well, and other runtimes are just catching up. Finally, writing an optimized runtime for any language is a huge endeavour. It requires lots of dev work and effort, which is quite expensive. Since web browsers make a ton of money and are backed by the richest companies around, and they care a lot about the performance of JavaScript in their browsers, there's actually an immense amount of investment made to the JS interpreter and virtual machines to have it be as efficient and optimized as can be. In practice it means that there exists JS VMs that outperform all of Ruby, Python, PHP, Perl, and almost all other dynamic programming language interpreter/VM out there. There's not many things that can rival that, you've got Go, JDK, .Net, GCC, and the Rust compiler maybe. The former because they've also had ton of money poured into them, and the latter because its entire language design and everything targets performance. Also you've got OCaml, Haskell, CommonLisp and Scheme runtimes of yore that might rival it due to how long they've had dedicated researchers and volunteers contribute. In any case, it means JS VMs are quite competitive performance wise.