"Instead of coding in one language, we're actually coding in two. One is the subset JavaScript that can be run in all browsers, and another is the set of JavaScript that can be run by Node. Knowing the difference between the two languages and context switching between them is simply a required skill. You know what would be awesome? If we wrote our libraries so that they could run either on the server or on the client, and they did so in a transparent way. Maybe it would help to give a concrete example of how this could be awesome." Isn't YUI trying to do this? Lots to catch up on