io.js has one major advantage over your other examples: it is tracking the same javascript that browsers are running. When every major browser is moving in the

io.js has one major advantage over your other examples: it is tracking the same javascript that browsers are running. When every major browser is moving in the same direction with a language, any server-side counterpart is best served moving in the same direction. Without browsers, io.js would have likely ended up in the same place as all the examples above.