For example, you want to know the number of years when books have been published.
data/books.yml:
- Book: "Book1"
Year: "2020"
- Book: "Book2"
Year: "2020"
- Book: "Book3"
Year: "2021"
template:
{{ $scratch := newScratch }}
{{ range .Site.Data.books }}
{{ $scratch.Add "years" (slice .Year) }}
{{ end }}
{{ len ($scratch.Get "years" | uniq) }}
This will return 2, as books have been published in 2020 and 2021.