To the contrary, JavaScript is one of the most portable and backward-compatible languages of all time. Portability and long-term maintenance on node.js is excellent if you stick to long-term development practices (commonjs, es5) and few core packages such as express.js. The only weak spot I encountered were subtle changes in error handling such as removal of auto-cleaning of resources with domain.dispose() back in v0.12 or v4 or so, and the somewhat unclear deprecation status of exception domains or the error handling/cleanup story in general, resp.