GitHub Pages can't run custom Jekyll plug-ins so when generating anchors for your headings (i.e. h1 - h6), you're stuck with JavaScript solutions that will inject anchors. But what if your users don't have JavaScript enabled on their browsers? If you're building a static website, why not make your anchors static as well?
As a part of my "Pure Liquid" series of Jekyll snippets, here is a Liquid snippet that will modify your generated HTML to inject anchors. Want to see it in action? Here are some awesome websites that I know of using this solution ❤️.
- Travis CI Docs (fixed in #1960)
- Bitrise's Documentation
- di's personal website
- sitespeed.io
- Duality's developer docs
- Australia's Vote Flux campaign
- mlpack.org
- Riot.js website
- "Just the Docs" Jekyll theme
- Microsoft's TypeScript website
- VMWare's Octant documentation
Want a Table of Contents in your Jekyll layouts without JavaScript or a plug-in?
Check out the sister project over at allejo/jekyll-toc.
Alright, so how do you use it?
-
Download the latest
anchor_headings.html -
Toss that file in your
_includesfolder -
Where you typically would put
{{ content }}in your layout, you would instead use this Liquid tag to output your page's content:{% include anchor_headings.html html=content anchorBody="#" %}
If this snippet is used in a layout that is inherited by a child layout, it will apply to the child layout as well. If the child layout uses this snippet in addition to the parent layout, then heading anchors will be duplicated. You should only use this snippet in one layout.
You may remove anchorBody and add an icon via CSS' content property instead. You may also use HTML in anchorBody and add screen reader friendly markup.
Take a look at the unit tests directory for more examples of how to use this script.
This snippet is highly customizable. Here are the available parameters to change the behavior of the snippet.
| Parameter | Type | Default | Description |
|---|---|---|---|
html |
string | * | the HTML of compiled markdown generated by kramdown in Jekyll |
beforeHeading |
bool | false | Set to true if the anchor should be placed before the heading's content |
anchorAttrs |
string | '' | Any custom HTML attributes that will be added to the <a> tag; you may NOT use href, class or title; the %heading% placeholder is available |
anchorBody |
string | '' | The content that will be placed inside the anchor; the %heading% placeholder is available |
anchorClass |
string | '' | The class(es) that will be used for each anchor. Separate multiple classes with a space |
anchorTitle |
string | '' | The title attribute that will be used for anchors; the %heading% placeholder is available |
h_min |
int | 1 | The minimum header level to build an anchor for; any header lower than this value will be ignored |
h_max |
int | 6 | The maximum header level to build an anchor for; any header greater than this value will be ignored |
bodyPrefix |
string | '' | Anything that should be inserted inside of the heading tag before its anchor and content |
bodySuffix |
string | '' | Anything that should be inserted inside of the heading tag after its anchor and content |
* This is a required parameter
The performance impact of this snippet on your site is pretty negligible. The stats below were gotten from Jekyll's --profile option.
Filename | Count | Bytes | Time
-------------------------------------------------+-------+----------+------
# performance on docs.travis-ci.com from ~Aug 2018
_includes/anchor_headings.html | 193 | 1667.96K | 0.695
This snippet may be redistributed under the MIT license.
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