complement
Syntax
complement COLLECTION [COLLECTION]...
collections.Complement COLLECTION [COLLECTION]...
To find the elements within $c3 that do not exist in $c1 or $c2:
{{ $c1 := slice 3 }}
{{ $c2 := slice 4 5 }}
{{ $c3 := slice 1 2 3 4 5 }}
{{ complement $c1 $c2 $c3 }} → [1 2]
{{ $c3 | complement $c1 $c2 }} → [1 2]
You can also use the complement function with page collections. Let’s say your site has five content types:
content/
├── blog/
├── books/
├── faqs/
├── films/
└── songs/
To list everything except blog articles (blog) and frequently asked questions (faqs):
{{ $blog := where site.RegularPages "Type" "blog" }}
{{ $faqs := where site.RegularPages "Type" "faqs" }}
{{ range site.RegularPages | complement $blog $faqs }}
<a href="{{ .RelPermalink }}">{{ .LinkTitle }}</a>
{{ end }}
{{ range where site.RegularPages "Type" "not in" (slice "blog" "faqs") }}
<a href="{{ .RelPermalink }}">{{ .LinkTitle }}</a>
{{ end }}
In this example we use the complement function to remove stop words from a sentence:
{{ $text := "The quick brown fox jumps over the lazy dog" }}
{{ $stopWords := slice "a" "an" "in" "over" "the" "under" }}
{{ $filtered := split $text " " | complement $stopWords }}
{{ delimit $filtered " " }} → The quick brown fox jumps lazy dog