hugo/content/en/functions/collections/Union.md

title	description	categories	keywords	action	aliases
collections.Union	Given two arrays or slices, returns a new array that contains the elements that belong to either or both arrays/slices.			aliases related returnType signatures union functions/collections/Complement functions/collections/Intersect functions/collections/SymDiff functions/collections/Union any collections.Union SET1 SET2	/functions/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) }}
<!-- returns [1 2 3 4 5] -->

{{ union (slice 1 2 3) nil }}
<!-- returns [1 2 3] -->

{{ union nil (slice 1 2 3) }}
<!-- returns [1 2 3] -->

{{ union nil nil }}
<!-- returns an error because both arrays/slices have to be of the same type -->

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.