Templating

GitBook uses the Nunjucks templating language to process pages and theme's templates.

The Nunjucks syntax is very similar to Jinja2 or Liquid. Its syntax uses surrounding braces { } to mark content that needs to be processed.

Variables

A variable looks up a value from the template context. If you wanted to simply display a variable, you would use the {{ variable }} syntax. For example :

My name is {{ name }}, nice to meet you

This looks up username from the context and displays it. Variable names can have dots in them which lookup properties, just like JavaScript. You can also use the square bracket syntax.

{{ foo.bar }}
{{ foo["bar"] }}

If a value is undefined, nothing is displayed. The following all output nothing if foo is undefined: {{ foo }}, {{ foo.bar }}, {{ foo.bar.baz }}.

GitBook provides a set of predefined variables from the context.

Filters

Filters are essentially functions that can be applied to variables. They are called with a pipe operator (|) and can take arguments.

{{ foo | title }}
{{ foo | join(",") }}
{{ foo | replace("foo", "bar") | capitalize }}

The third example shows how you can chain filters. It would display "Bar", by first replacing "foo" with "bar" and then capitalizing it.

Tags

if

if tests a condition and lets you selectively display content. It behaves exactly as JavaScript's if behaves.

{% if variable %}
  It is true
{% endif %}

If variable is defined and evaluates to true, "It is true" will be displayed. Otherwise, nothing will be.

You can specify alternate conditions with elif and else:

{% if hungry %}
  I am hungry
{% elif tired %}
  I am tired
{% else %}
  I am good!
{% endif %}

for

for iterates over arrays and dictionaries.

# Chapters about GitBook

{% for article in glossary.terms['gitbook'].articles %}
* [{{ article.title }}]({{ article.path }})
{% endfor %}

set

set lets you create/modify a variable.

{% set softwareVersion = "1.0.0" %}

Current version is {{ softwareVersion }}.
[Download it](website.com/download/{{ softwareVersion }})

include and block

Inclusion and inheritance is detailled in the Content References section.

Escaping

If you want GitBook to ignore any of the special templating tags, you can use raw and anything inside of it will be output as plain text.

{% raw %}
  this will {{ not be processed }}
{% endraw %}