collections.Union

Returns a slice containing the unique elements from two given slices.

Syntax

collections.Union SLICE1 SLICE2

Returns

[]any

Alias

union

{{ 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.

Last updated: February 8, 2026 : content: Improve descriptions and signatures for collections functions (573b8610f)

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