This is a nifty use of Service Workers—using a cache to mitigate unresponsive Content Delivery Networks.
The stuff in here about Promise.race is particularly useful for “lie-fi” scenarios: instead of thinking about the network connection in a binary way (either it’s available or it isn’t), considering the scenario of a crappy network connection seems more realistic.
Web developers overwhelmingly rejected the draconian error-handing of XML …and yet today, web developers are embracing that very same error-handling model by rendering everything with JavaScript.
I don’t think it’s the way of the web to have your site fail and show a blank screen because some third-party dependency doesn’t load, JavaScript is turned off or because your developer left a trailing comma in a JavaScript object and didn’t test in Internet Explorer.
A great set of slides from Nicholas, all about the disturbing trend in “modern” web apps to depend entirely on JavaScript as a single point of failure.