Generally, you can trust the API endpoints your application is connecting to, but there is always a chance that those services could go down. It is good to have a plan B for situations such as this. In this recipe, we are going to use the service worker to provide us with a fallback response in such a situation.
To get started with service workers, you will need to have the service worker experiment feature turned on in your browser settings. If you have not done this yet, refer to the first recipe of Chapter 1, Learning Service Worker Basics: Setting up service workers. Service workers only run across HTTPS. To find out how to set up a development environment to support this feature, refer to the following recipes: Setting up GitHub pages for SSL, Setting up SSL for Windows, and Setting up SSL for Mac.
Follow these instructions to set up your file structure:
Download all the files from the following location: