Depends a great deal on what the application is, I think. If you're doing heavy lifting (or anything a bit complicated) in the client and then need to make simi

Depends a great deal on what the application is, I think. If you're doing heavy lifting (or anything a bit complicated) in the client and then need to make similar functionality available to APIs offline it's a godsend. My current hobby project is a kind of REPL/programming language that does all of its compute in the client, and being able to hit a button and export a "serverless" microservice is lovely side-effect of being able to run JS on the server. It isn't exactly "the backend" to my application, more "a headless client exposed to the net," though, I guess. (As someone new to JS, the frigging Node ".mjs" fiasco almost derailed the whole thing, though... What were they thinking?) Edit: oh, and "optimistic rendering" is also a big win -- if you can show the result of an action before it has persisted (or preview it before the user has done it) shared code can also come in handy. Though perhaps we're too scared of network round-trip times.