hugo/docs/content/templates/functions.md

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/layout/functions/	2013-07-01	Functions	main parent layout	/templates/variables	/templates/go-templates	Hugo Template Functions	20

Hugo uses the excellent Go html/template library for its template engine. It is an extremely lightweight engine that provides a very small amount of logic. In our experience it is just the right amount of logic to be able to create a good static website.

Go templates are lightweight but extensible. Hugo has added the following functions to the basic template logic.

(Go itself supplies built-in functions, including comparison operators and other basic tools; these are listed in the Go template documentation.)

General

isset

Return true if the parameter is set. Takes either a slice, array or channel and an index or a map and a key as input.

e.g. {{ if isset .Params "project_url" }} {{ index .Params "project_url" }}{{ end }}

echoParam

If parameter is set, then echo it.

e.g. {{echoParam .Params "project_url" }}

eq

Return true if the parameters are equal.

e.g. {{ if eq .Section "blog" }}current{{ end}}"

first

Slices an array to only the first X elements.

Works on lists, taxonomies, terms, groups

e.g. {{ range first 10 .Data.Pages }} {{ .Render "summary"}} {{ end }}

where

Filters an array to only elements containing a matching value for a given field.

Works on lists, taxonomies, terms, groups

e.g.

{{ range where .Data.Pages "Section" "post" }}
   {{ .Content}}
{{ end }}

where and first can be stacked

e.g.

{{ range first 5 (where .Data.Pages "Section" "post") }}
   {{ .Content}}
{{ end }}

in

Checks if an element is in an array (or slice) and returns a boolean. The elements supported are strings, integers and floats (only float64 will match as expected). In addition, it can also check if a substring exists in a string.

e.g. {{ if in .Params.tags "Git" }}Follow me on GitHub!{{ end }} or {{ if in "this string contains a substring" "substring" }}Substring found!{{ end }}

intersect

Given two arrays (or slices), this function will return the common elements in the arrays. The elements supported are strings, integers and floats (only float64).

A useful example of this functionality is a 'similar posts' block. Create a list of links to posts where any of the tags in the current post match any tags in other posts.

e.g.

{{ $page_link := .Permalink }} {{ $tags := .Params.tags }} {{ range .Site.Recent }} {{ $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 }}

Math

add

Adds two integers.

e.g. {{add 1 2}} → 3

sub

Subtracts two integers.

e.g. {{sub 3 2}} → 1

div

Divides two integers.

e.g. {{div 6 3}} → 2

mul

Multiplies two integers.

e.g. {{mul 2 3}} → 6

mod

Modulus of two integers.

e.g. {{mod 15 3}} → 0

modBool

Boolean of modulus of two integers. true if modulus is 0.

e.g. {{modBool 15 3}} → true

Strings

urlize

Takes a string and sanitizes it for usage in URLs, converts spaces to "-".

e.g. <a href="/tags/{{ . | urlize }}">{{ . }}</a>

safeHtml

Declares the provided string as "safe" so Go templates will not filter it.

e.g. {{ .Params.CopyrightHTML | safeHtml }}

lower

Convert all characters in string to lowercase.

e.g. {{lower "BatMan"}} → "batman"

upper

Convert all characters in string to uppercase.

e.g. {{upper "BatMan"}} → "BATMAN"

title

Convert all characters in string to titlecase.

e.g. {{title "BatMan"}} → "Batman"

highlight

Take a string of code and a language, uses Pygments to return the syntax highlighted code in HTML. Used in the highlight shortcode.