Christian Heilmann

Quick Tip: How to capture and replace newlines in liquid for Jekyll/GitHub Pages

Thursday, December 17th, 2020 at 1:40 pm

As part of the re-write of The Developer Advocacy Handbook I needed to have blockquotes with different classes.

Fact display in the book

With GitHub Pages markdown you can do that using the > notation:

> **Fact:** There are no bad students or a bad audience --
only bad workshops and talks. Your mood, dedication and
enthusiasm do become those of the audience -- 
if you are not happy, they won\'t be happy.

The problem was that I couldn’t add CSS classes to the blockquote elements so I can show them in different styles. I wanted four of them: example, fact, warning and tip.

The good news is that even without any styling using the strong name should make it obvious. But as there is no text “contains” selector in CSS I couldn’t rely on that to change the blockquote element.

First solution: JavaScript

The first thing I thought was to use JavaScript to apply the classes, which is pretty straight forward:

let bqs = document.querySelectorAll('blockquote');
  bqs.forEach(b => {
  b.className = b.
    querySelector('strong').
      innerText.
        toLowerCase().
          replace(':','');
});

This, however, felt dirty and I wanted to use the system itself to do that task.

Moving to liquid

So I wrote a liquid include to convert the HTML before rendering. In my layout template, this works by replacing the {{ content }} with {% include blockquotes.html html=content %}.

In the blockquotes.html, I thought it’d be easy to do a search and replace. Alas, there is the issue that liquid only does string replacement and doesn’t know any regular expressions.

The HTML generated from the markdown has a line-break in it:

<blockquote>
  <p><strong>Fact:</strong> There are no bad students … </p>
</blockquote>

This is where it didn’t get fun. The replace filter doesn’t allow you to concatenate strings and doesn’t know the concept of n. So, I tried to use the newline_to_br together with strip_newlines filters and then replace the br but it was messy.

Turns out, the main trick was to capture a newline in liquid and assemble the string to replace using that one.

{% capture newline %}
{% endcapture %}
{% capture tip %}<blockquote>{{newline}}  <p><strong>Tip:</strong>{% endcapture%}
{% capture example %}<blockquote>{{newline}}  <p><strong>Example:</strong>{% endcapture%}
{% capture warning %}<blockquote>{{newline}}  <p><strong>Warning:</strong>{% endcapture%}
{% capture fact %}<blockquote>{{newline}}  <p><strong>Fact:</strong>{% endcapture%}
 
{% assign newhtml = include.html | 
  replace: tip, '<blockquote class="tip"><p><strong>Tip:</strong>' |
  replace: example, '<blockquote class="example"><p><strong>Example:</strong>' |
  replace: warning, '<blockquote class="warning"><p><strong>Warning:</strong>' |
  replace: fact, '<blockquote class="fact"><p><strong>Fact:</strong>' 
%}
{{ newhtml }}

This works fine. Seems superfluous, but it is a way. It might be that there is a much simpler way as I am new to this world, having used PHP before the build the old version of the book. Got a better option? Tell me :)

Share on Twitter