Go to about:serviceworkers and ctrl-f twitter and remove every instance. That will fix it.
So there's a persistent cache of javascript that can't be cleared except one at a time? My cache is full of fly-by-night websites. Surely this is a shocking privacy hole?
Web browsers need to be more transparent about what state they are storing, and more accommodating of attempts to clear it.
Also a performance/battery suck. Apple refuses to implement it in Safari, and it's one of the big reasons web developers deride Safari for being "the new IE"
In the wider concept of "PWA" (Progressive Web Apps), they also are used to enable webapps to act a bit like local apps if the user opts in - a user can add them to the homescreen, and they then are launched just like normal apps (but still sandboxed in the browser). An example that does this quite well is the Web-IRC client "The Lounge" - you can open and use it in the browser, but also pin it as a standalone app, including support for push notifications etc if you allow that.
That's far from obvious. Good cache control and offline usage are great for battery usage.
> Apple refuses to implement it in Safari
Wrong, Safari supports them. What Apple doesn't do well is enabling webapps that you pin to your homescreen ("PWAs") to work (they allow it, but from what I hear it's buggy and has weird restrictions), because they'd rather force you to make a native app.
AFAIK it's fine because they get cleared when you delete cookies/site data, so it's no worse than a site using localstorage, for instance.
I agree with the transparency, I was not aware about service workers until this post. In the meantime, there are Firefox/Chrome extensions that manages the service workers. Those extension can block service workers from installing without the user consent which that was nice.