Context Specific Assets with Jekyll

asset.html

{%- capture type -%}
  {%- if page.layout == "post" -%}
    posts
  {%- elsif page.collection -%}
    {{ page.collection }}
  {%- else -%}
    pages
  {%- endif -%}
{%- endcapture -%}

{%- capture context -%}
  {%- if page.layout == "post" -%}
    {{ page.path | split:"/" | last | split:"." | first }}
  {%- else -%}
    {{ page.title | slugify }}
  {%- endif -%}
{%- endcapture -%}

{{ site.url }}{{ site.baseurl }}/assets/{{ type }}/{{ context }}/{{ include.file }}

example-post.html

---
include:
  css: styles.css
  js:
  - library.js
  - scripts.js
---

{% include asset.html file="filename.ext" %}

footer.html

{% if page.include.js %}
  {% for file in page.include.js %}
  <script src="{% include asset.html file=file %}"></script>
  {% endfor %}
{% endif %}

header.html

{% if page.include.css %}
  {% for file in page.include.css %}
  <link rel="stylesheet" href="{% include asset.html file=file %}">
  {% endfor %}
{% endif %}