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50 lines
1.5 KiB
Markdown
50 lines
1.5 KiB
Markdown
---
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title: union
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# linktitle: union
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description: Given two arrays or slices, returns a new array that contains the elements or objects that belong to either or both arrays/slices.
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godocref:
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date: 2017-02-01
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publishdate: 2017-02-01
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lastmod: 2017-03-12
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categories: [functions]
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menu:
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docs:
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parent: "functions"
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#tags: [filtering,lists]
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signature: ["union SET1 SET2"]
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workson: []
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hugoversion: 0.20
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relatedfuncs: [intersect,where]
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deprecated: false
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aliases: []
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---
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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. The elements supported are strings, integers, and floats (only float64).
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```golang
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{{ union (slice 1 2 3) (slice 3 4 5) }}
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<!-- returns [1 2 3 4 5] -->
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{{ union (slice 1 2 3) nil }}
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<!-- returns [1 2 3] -->
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{{ union nil (slice 1 2 3) }}
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<!-- returns [1 2 3] -->
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{{ union nil nil }}
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<!-- returns an error because both arrays/slices have to be of the same type -->
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```
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This is also very useful to use as `OR` filters when combined with where:
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```html
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{{ $pages := where .Site.RegularPages "Type" "not in" (slice "page" "about") }}
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{{ $pages := $pages | union (where .Site.RegularPages "Params.pinned" true) }}
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{{ $pages := $pages | intersect (where .Site.RegularPages "Params.images" "!=" nil) }}
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```
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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.
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See [intersect](/functions/intersect) for `AND`.
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