You can write JS functionally but to get the benefits from the video like modeling your data as sum & product types as well as static type checking, you need to

You can write JS functionally but to get the benefits from the video like modeling your data as sum & product types as well as static type checking, you need to use a language with its own compiler. For languages that compile to JS, Elm looks a bit more like the F# in the video (https://elm-lang.org/ https://elm-lang.org/) and Typescript (https://www.typescriptlang.org/ https://www.typescriptlang.org/) is a much more like standard JS.