Previous Next Links for Jekyll Collections

jekyll-collections-prev-next.html

{% capture the_collection %}{{page.collection}}{% endcapture %}
  {% if page.collection %}
    {% assign  document = site[the_collection]  %}
  {% endif %}
<h1>TITLE: {{ page.title }}</h1>
{% for links in document  %}
  {% if links.title == page.title %}
    {% unless forloop.first %}
      {% assign prevurl = prev.url %}
    {% endunless %}
    {% unless forloop.last %}
      {% assign next = document[forloop.index] %}
      {% assign nexturl = next.url %}
    {% endunless %}
  {% endif %}
  {% assign prev = links %}
{% endfor %}

<script>
document.body.onkeyup = function(e){
if (e.keyCode == '37') { window.location = '{{prevurl}}'; }
if (e.keyCode == '39') { window.location = '{{nexturl}}'; }
};
</script>

{% if prevurl %}<a href="{{prevurl}}" class="prev">PREV {{prevurl}}</a>{% endif %}<br />

{% if nexturl %}<a href="{{nexturl}}" class="nxt">Next {{nexturl}}</a>{% endif %}

This still works in 2019! However, Jekyll collections (that generate pages with output: true at least) seem to have the built-in page.previous and page.next variables, too, so you may not need this.

See any guide on using those variables for posts. It should apply.