[saidajigumi]

First off, while some sharing between client and server happens, that tends to be an edge case in my experience. The roles of client and server, and APIs available to each, are rather different. I.e. the environment of the browser and node.js server aren't homogenous.

Second, "start coding in XXX without learning a new language" is a terrible selling point. I've seen this thinking appeal to misguided PHB-types and witnessed the result: immense organizational damage. In my experience, this isn't a necessary or sufficient selling point to good developers. Learning a new language just isn't that hard, and a big part of a shift like this is actually in learning the new environment's paradigms, APIs, and best practices.

To make the latter point more strongly: if you're having doubts about your ability to pick up a new language, definitely take some time to learn a few new languages. Do a tutorial, play with a few small projects, enough to get the flavor of the language. Your hackery will benefit immensely from this, even when you return to your primary language.