Add anchor links

_includes/anchor_headings.html

@@ -0,0 +1,97 @@
+{% capture headingsWorkspace %}
+  {% comment %}
+    Version 1.0.1
+      https://github.com/allejo/jekyll-anchor-headings
+
+    "Be the pull request you wish to see in the world." ~Ben Balter
+
+    Usage:
+      {% include anchor_headings.html html=content %}
+
+    Parameters:
+      * html          (string) - the HTML of compiled markdown generated by kramdown in Jekyll
+
+    Optional Parameters:
+      * beforeHeading (bool)   : false  - Set to true if the anchor should be placed _before_ the heading's content
+      * 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
+      * 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
+
+    Output:
+      The original HTML with the addition of anchors inside of all of the h1-h6 headings.
+  {% endcomment %}
+
+<!-- We need a newline character, so the lack of indentation here is important -->
+{% capture new_line %}
+{% endcapture %}
+
+  {% assign minHeader = include.h_min | default: 1 %}
+  {% assign maxHeader = include.h_max | default: 6 %}
+  {% assign beforeHeading = include.beforeHeading %}
+  {% assign nodes = include.html | split: '<h' %}
+
+  {% capture edited_headings %}{% endcapture %}
+
+  {% for node in nodes %}
+    {% if node == "" %}
+      {% continue %}
+    {% endif %}
+
+    {% assign headerLevel = node | replace: '"', '' | slice: 0, 1 | times: 1 %}
+
+    <!-- If the node doesn't have a header, then it's content before the first heading; don't discard it -->
+    {% if headerLevel < 1 or headerLevel > 6 %}
+      {% capture edited_headings %}{{ edited_headings }}{{ node }}{% endcapture %}
+      {% continue %}
+    {% endif %}
+
+    {% assign _workspace = node | split: '</h' %}
+    {% assign _idWorkspace = _workspace[0] | split: 'id="' %}
+    {% assign _idWorkspace = _idWorkspace[1] | split: '"' %}
+    {% assign html_id = _idWorkspace[0] %}
+
+    {% capture _hAttrToStrip %}{{ _workspace[0] | split: '>' | first }}>{% endcapture %}
+    {% assign header = _workspace[0] | replace: _hAttrToStrip, '' %}
+
+    <!-- Build the anchor to inject for our heading -->
+    {% capture anchor %}{% endcapture %}
+
+    {% if html_id and headerLevel >= minHeader and headerLevel <= maxHeader %}
+      {% capture anchor %}href="#{{ html_id}}"{% endcapture %}
+
+      {% if include.anchorClass %}
+        {% capture anchor %}{{ anchor }} class="{{ include.anchorClass }}"{% endcapture %}
+      {% endif %}
+
+      {% if include.anchorTitle %}
+        {% capture anchor %}{{ anchor }} title="{{ include.anchorTitle | replace: '%heading%', header }}"{% endcapture %}
+      {% endif %}
+
+      {% capture anchor %}<a {{ anchor }}>{{ include.anchorBody | replace: '%heading%', header | default: '' }}</a>{% endcapture %}
+
+      <!-- In order to prevent adding extra space after a heading, we'll let the 'anchor' value contain it -->
+      {% if beforeHeading %}
+        {% capture anchor %}{{ anchor }} {% endcapture %}
+      {% else %}
+        {% capture anchor %} {{ anchor }}{% endcapture %}
+      {% endif %}
+    {% endif %}
+
+    {% capture new_heading %}
+      <h{{ _hAttrToStrip }}
+        {{ include.bodyPrefix }}
+        {% if beforeHeading %}
+          {{ anchor }}{{ header }}
+        {% else %}
+          {{ header }}{{ anchor }}
+        {% endif %}
+        {{ include.bodySuffix }}
+      </h{{ _workspace | last }}
+    {% endcapture %}
+    {% capture edited_headings %}{{ edited_headings }}{{ new_heading | replace: '  ', '' | replace: new_line, '' }}{{ new_line }}{% endcapture %}
+  {% endfor %}
+{% endcapture %}{% assign headingsWorkspace = '' %}{{ edited_headings | strip }}

_layouts/post.html

@@ -6,4 +6,4 @@ <h1>{{ page.title }}</h1>
   <small>{{ page.date | date : "%B %d %Y"}}</small>
 </div>
 
-{{ content }}
+{% include anchor_headings.html html=content anchorBody="#" anchorClass="anchor" %}

assets/css/style.css

@@ -101,3 +101,17 @@ td p {
     padding: 0px;
   }
 }
+
+.anchor {
+  visibility: hidden;
+  color: #dfe2e5;
+}
+
+h1:hover .anchor,
+h2:hover .anchor,
+h3:hover .anchor,
+h4:hover .anchor,
+h5:hover .anchor,
+h6:hover .anchor {
+  visibility: visible;
+}