What are some advantages to using a Javascript-based server over a non-Javascript server?

Disclaimer: This question will be a bit open-ended. I also expect replies to be partly based off of developer preference.

I've been doing some research lately on Express.js (coupled via Node.js) and I'm struggling to find how I would fit either of these technologies into my current workflow for developing websites. Lately I've been working in either Wordpress or Ruby on Rails, the prior will run on Apache, the latter will run on it's own proprietary server (I assume).

Now perhaps I'm just not understanding something, but I fail to see the advantages to enlisting the support of a Javascript-based framework/server. If there are clear cut advantages to making this part of my workflow, what would they be? I haven't been able to find any ways to fit this into (per say) a Rails application or a Wordpress site. Could someone point me in the direction of some better help of implementing these technologies on top of ones I already use?

One last question, what happens if someone has Javascript disabled in their browser? How would a Javascript-based server react (if at all)?

There are two big differences:

Event loop

Node.js is a bit different from the usual Apache concept, because of the way it handles connections. Instead of having synchronous connections, Node uses an event loop to have non-blocking operations. Note that this is not unique to Javascript and there are C and Python based frameworks that also enable a similar event loop approach, however in Javascript it's probably the most natural feeling since this is how JS has worked since it was introduced.

Supposedly, this should enable you to handle more concurrent clients. However, it hasn't had as much real world exposure as the regular blocking solutions so this approach isn't as mature as most current implementations. The actual performance difference is questionable as it depends on the exact requirements for the application.

Code Sharing

This point is much less controversial than the previous difference, but in essence if you have the same language on both the client and the server, you can reuse a lot of the code, instead of having to rewrite your data structures etc in multiple languages, saving you a lot of development time. However, you have to understand that the concepts of server side JS are different from what you know on the browser, such as you don't have dynamic JS with jQuery or Prototype, but it's result and use-cases are more similar to what PHP is widely used for.

The primary advantage of having Javascript as your server-side language is that you're writing your whole system in a single language.

This has advantages in terms of:

  • Learning curve and mental context switching for the developer
  • and also in provides some possibility for sharing code between the two environments.

However, this last point is less helpful than it sounds, for a number of reasons, and this is where the disadvantages come in:

  • Not much code can actually be shared, because of the differences in what the two environments are actually doing. Maybe a bit of validation code, so you know that you're doing the same checks on both client and server, and maybe a few utility functions, but that's about it.
  • The libraries you use will be completely different between the two as well: jQuery only works on the client, and Node has libraries that are server-specific.
  • So as a developer, you still need to mentally context switch between environments, because the two environments are different. They may share a language, but their modes of operation are different, and what they do is different. In fact, sharing the language between the two can actually make it harder to context switch, and this can lead to errors.
  • Finally, it's worth bearing in mind that while Node is getting lots of attention from the developer community, it is still new and evolving quickly: if you're a business considering a it as a development platform, it's probably not quite yet stable enough to base a major project on.