Add optional table of contents for blog posts

Author: danyspin97

exampleSite/config.toml

@@ -42,6 +42,7 @@ posts_navigation = true
 # issoHost = "comments.domain.tld:1234"
 # githubRepo = "githubUsername/repositoryName/tree/master"
 small_banner_logo = false
+tableofcontents = true
 
 [params.colors]
 identifier = "#527fc1f"

layouts/partials/blog_single.html

@@ -45,6 +45,9 @@
                 </div>
             </div>
             <div class="markdown">
+                {{ if .Params.toc | default false }}
+                    {{ partial "table_of_contents.html" . }}
+                {{ end }}
                 {{ partial "content" . }}
             </div>
             {{ if .Site.Params.share }}

layouts/partials/table_of_contents.html

@@ -0,0 +1,22 @@
+{{/* https://gist.github.com/skyzyx/a796d66f6a124f057f3374eff0b3f99a */}}
+{{/* https://github.com/gohugoio/hugo/issues/1778 */}}
+
+{{/* ignore empty links with + */}}
+{{ $headers := findRE "<h[1-4].*?>(.|\n])+?</h[1-4]>" .Content }}
+{{ .Scratch.Set "last_level" 1 }}
+
+{{/* at least one header to link to */}}
+{{ $has_headers := ge (len $headers) 1 }}
+{{ if $has_headers }}
+<aside class="table-of-contents">
+    <ul class="toc-h{{ . }}">
+    {{ range $headers }}
+        {{ $header := . }}
+        {{ $base := ($.Page.File.LogicalName) }}
+        {{ $anchorId := ($header | plainify | htmlUnescape | anchorize) }}
+        {{ $href := delimit (slice $base $anchorId) "#" | string }}
+         <li><a href="{{ relref $.Page $href }}">{{ $header | plainify | htmlUnescape }}</a></li>
+    {{ end }}
+    </ul>
+</aside>
+{{ end }}