hugo-theme-stack/layouts/post/single.html

{{ .Scratch.Set "hasTOC" (ge (len .TableOfContents) 100) }}
{{ define "body-class" }}article-page keep-sidebar{{ if .Scratch.Get "hasTOC" }} has-toc{{ end }}{{ end }}
{{ define "container-class" }}extended{{ end }}
{{ define "main" }}
    {{ partial "article/article.html" . }}

    {{ partial "article/components/related-contents" . }}
     
    {{ if or (not (isset .Params "comments")) (eq .Params.comments "true")}} 
        {{ partial "comments/include" . }}
    {{ end }}

    {{ partialCached "footer/footer" . }}

    {{ partialCached "article/components/photoswipe" . }}
{{ end }}

{{ define "left-sidebar" }}
    {{ if .Scratch.Get "hasTOC" }}
        <div id="article-toolbar">
            <a href="{{ .Site.BaseURL }}" class="back-home">
                {{ (resources.Get "icons/back.svg").Content | safeHTML }}
                <span>Back</span>
            </a>
        </div>
    {{ else }}
        {{ partial "sidebar/left.html" . }}
    {{ end }}
{{ end }}

{{ define "right-sidebar" }}
    {{ if .Scratch.Get "hasTOC" }}
        <aside class="sidebar right-sidebar sticky">
            <section class="widget archives">
                <div class="widget-icon">
                    {{ partial "helper/icon" "hash" }}
                </div>
                <h2 class="widget-title section-title">Table of contents</h2>
                
                <div class="widget--toc">
                    {{ .TableOfContents }}
                </div>
            </section>
        </aside>
    {{ end }}
{{ end }}