Honestly speaking a lot of the list pointed out in the article is weird that way. For example, "Checks if function bodies that are implemented in the browser co

Honestly speaking a lot of the list pointed out in the article is weird that way. For example, "Checks if function bodies that are implemented in the browser contain [native code] when stringified" - that's a very straightforward way to check if a particular feature is browser-supported or was polyfilled.