Consider this page: https://firebase.google.com/docs/database/web/lists-of-data
Each snippet in the page is dynamically included from the source in this repository, in this case mostly from this file: https://github.com/firebase/snippets-web/blob/master/database/lists-of-data.js
Each snippet has a "region tag" which is defined by
// [START tag] and
// [END tag] comments. The code between the tags can be included in our documentation. Keeping the code on GitHub, rather than hard-coded into the HTML of our documentation, allows us to ensure the code is correct and up to date.