hugo/docs/content/en/functions/intersect.md

title	linktitle	description	godocref	date	publishdate	lastmod	categories	menu	keywords	signature	workson	hugoversion	relatedfuncs	deprecated	aliases
intersect	intersect	Returns the common elements of two arrays or slices.		2017-02-01	2017-02-01	2017-02-01	functions	docs parent functions		intersect SET1 SET2				false

The elements supported are strings, integers, and floats (only float64).

A useful example of intersect functionality is a "related posts" block. isset allows us to create a list of links to other posts that have tags that intersect with the tags in the current post.

The following is an example of a "related posts" partial template that could be added to a single page template:

{{< code file="layouts/partials/related-posts.html" download="related-posts.html" >}}

{{ $page_link := .Permalink }} {{ $tags := .Params.tags }} {{ range .Site.Pages }} {{ $page := . }} {{ $has_common_tags := intersect $tags .Params.tags | len | lt 0 }} {{ if and $has_common_tags (ne $page_link $page.Permalink) }}
• {{ $page.Title }}
{{ end }} {{ end }}

{{< /code >}}

This is also very useful to use as AND 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 params.

See union for OR.