CSS Tutorial – A (terrible?) way to do footnotes in HTML

Rengga Dev – Terence Eden poked around with a way to do footnotes using the <details>/<summary> elements. I think it’s kind of clever. Rather than a hyperlink that jumps down to explain the footnote elsewhere, the details are right there next to the text. I like that proximity in the code. Plus, you get the native open/close interactivity of the disclosure widget.

It’s got some tricky parts though. The <details> element is block-level, so it needs to become inline to be the footnote, and sized/positioned to look “right.” I think it’s a shame that it won’t sit within a <p> tag, so that makes it impractical for my own usage.

Craig Shoemaker in the comments forked the original to fiddle with the CSS, and that inspired me to do the same.

Rather than display the footnote text itself right inline (which is extra-tricky), I moved that content to a fixed-position location at the bottom of the page:

<div class="fake-p">
  The most cited work in history, for example, is a 1951 paper<details>
    <summary>1</summary>
    <div class="details-content">Lowry, O. H., Rosebrough, N. J., Farr, A. L. & Randall, R. J. J. Biol. Chem. 193, 265–275 (1951).</div>
  </details> describing an assay to determine the amount of protein in a solution.
</div>

<div class="fake-p">
  Sunlight poured like molten gold<details>
    <summary>2</summary>
    <div class="details-content">Not precisely, of course. Trees didn’t burst into flame, people didn’t suddenly become very rich and extremely dead, and the seas didn’t flash into steam. A better simile, in fact, would be ‘not like molten gold.’</div>
  </details> across the sleeping landscape.
</div>

<div class="fake-p">
  My blog was recently featured in an academic paper<details>
    <summary>3</summary>
    <div class="details-content"><span itemscope itemtype="http://schema.org/ScholarlyArticle"><span itemprop="citation"><span itemprop="author" itemscope itemtype="http://schema.org/Person"><span itemprop="name"><span itemprop="familyName">Eishita</span><span>, </span><span itemprop="givenName">Farjana Z.</span></span></span><span> & </span><span itemprop="author" itemscope itemtype="http://schema.org/Person"><span itemprop="name"><span itemprop="familyName">Stanley</span><span>, </span><span itemprop="givenName">Kevin G.</span></span></span><span> & </span><span itemprop="author" itemscope itemtype="http://schema.org/Person"><span itemprop="name"><span itemprop="familyName">Esquivel</span><span>, </span><span itemprop="givenName">Alain</span></span></span> <q><cite itemprop="headline">Quantifying the differential impact of sensor noise in augmented reality gaming input</cite></q> <span>(</span><time itemprop="datePublished" datetime="2015">2015</time><span>)</span> <span itemprop="publisher" itemscope itemtype="http://schema.org/Organization"><span itemprop="name">Institute of Electrical and Electronics Engineers (IEEE)</span></span><span>.</span> DOI: <a itemprop="url" href="https://doi.org/10.1109/gem.2015.7377202">https://doi.org/10.1109/gem.2015.7377202</a></span></span></div>
  </details> which pleased me greatly.
</div>

details,
summary {
  display: inline;
  vertical-align: super;
  font-size: 0.75rem;
  padding: 0 0.25rem;
}
summary {
  cursor: pointer;
}
.details-content {
  position: fixed;
  bottom: 0;
  left: 50%;
  transform: translateX(-50%);
  max-width: 90%;
  padding: 1rem;
  font-size: 1rem;
  background: lightyellow;
  box-shadow: 0 0 100px black;
  border-top-left-radius: 4px;
  border-top-right-radius: 4px;
}

/* Details don't like being inside a p */
.fake-p {
  margin: 0 0 1rem 0;
}

body {
  font: 100%/1.4 system-ui;
  margin: 0;
  padding: 2rem 2rem 20rem 2rem;
}

I’m not 100% convinced it’s a good idea, but I’m also not convinced it’s a terrible one.