Most of the popular frameworks generate a single JavaScript bundle that comprises an entire application. Some people break these bundles into multiple parts manually in a process called 'code-splitting' in order to do a really chunky kind of lazy load.

Code splitting via webpack is not a manual process.

Does your hand rolled framework handle minimization and obfuscation? Probably not because any changes would require a rebuild.

Are your assets cached? If they are, I'm curious how you handle the cache busting when a single file gets updated.

With HTTP/2, you can send files down independently, without creating a large bundle, so each file can be cached. You couldn’t obfuscate function names across files though unless you made the process deterministic based on module name.

But you need some cache-busting functionality anyways (otherwise how does the client know that file "something.js" has changed?

Etags could be used to cause the browser to revalidate the contents without too much overhead since the connection is already establishd, but good point.