ar.falsy.cat/layouts/partials/popover.html

<script>
  function htmlToElement(html) {
    const template = document.createElement('template')
    html = html.trim()
    template.innerHTML = html
    return template.content.firstChild
  }

  document.addEventListener("DOMContentLoaded", () => {
    [...document.getElementsByClassName("internal-link")]
      .forEach(li => {
        const linkDest = content[li.dataset.src]
        if (linkDest) {
          const popoverElement = `<div class="popover">
    <h3>${linkDest.title}</h3>
    <p>${removeMarkdown(linkDest.content).split(" ", 15).join(" ")}...</p>
</div>`
          const el = htmlToElement(popoverElement)
          li.appendChild(el)
          li.addEventListener("mouseover", () => {
            el.classList.add("visible")
          })
          li.addEventListener("mouseout", () => {
            el.classList.remove("visible")
          })
        }
      })
  })
</script>