Mostly React.js and Node.js, and I use NPM to install dependencies while I'm at the internet, and they still work when I go offline since they're downloaded.
The hard part is dealing with live APIs, but fortunately these can be recorded while online and replayed when offline, which seems like a good practice anyway during development.
> The hard part is dealing with live APIs, but fortunately these can be recorded while online and replayed when offline, which seems like a good practice anyway during development.
Just record the important parts of an HTTP request using your server software, such as Node.js, save them to disk, and replay them on matching subsequent requests when offline mode is enabled. Or use a high level library that already does this; I'm looking into yakbak[0x00].
The hard part is dealing with live APIs, but fortunately these can be recorded while online and replayed when offline, which seems like a good practice anyway during development.