In this recipe, we are going to learn how to cache resource files using a JSON file by specifying the names of the resource files in it. Usually, this is done by keeping an array in the service worker JavaScript file, but you might want them in a separate location, for reasons such as versioning, for example.
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 of Chapter 1, Learning Service Worker Basics: Setting up GitHub pages for SSL, Setting up SSL for Windows, and Setting up SSL for Mac.