collections.Union

Given two arrays (or slices) A and B, this function will return a new array that contains the elements or objects that belong to either A or to B or to both.

{{ union (slice 1 2 3) (slice 3 4 5) }} → [1 2 3 4 5]

{{ union (slice 1 2 3) nil }} → [1 2 3]

{{ union nil (slice 1 2 3) }} → [1 2 3]

{{ union nil nil }} → []

OR filter in where query

This is also very useful to use as OR filters when combined with where:

{{ $pages := where .Site.RegularPages "Type" "not in" (slice "page" "about") }}
{{ $pages = $pages | union (where .Site.RegularPages "Params.pinned" true) }}
{{ $pages = $pages | intersect (where .Site.RegularPages "Params.images" "!=" nil) }}

The above fetches regular pages not of page or about type unless they are pinned. And finally, we exclude all pages with no images set in Page parameters.

See intersect for AND.