A web component to add and position sibling anchor links for heading elements (h1–h6) when they have an id attribute.

Inspired by David Darnes’ <heading-anchors>.

• Demo on GitHub Pages

npm install @zachleat/heading-anchors

Include the heading-anchors.js file on your web site (via <script type="module">) and use <heading-anchors>.

• Useful when you want preserve heading text as is (selectable, able to nest other links, etc).
• Useful when you want to exclude anchor links from your RSS feed.
• Links are positioned alongside heading text, but not nested inside of headings (for improved screen-reader compatibility and accessibility)
• Establishes a placeholder element to establish space for the anchor link and so that heading text doesn’t reflow during interaction
• Prefers the CSS Anchoring API (where available) but works using JavaScript positioning when the API is not available.
• Automatically matches font styling of the heading (font-family, line-height, font-size, and font-weight)

• Use the selector attribute to change the headings used, e.g. <heading-anchors selector="h2,h3,h4">
  • Default: h2,h3,h4,h5,h6
• Internationalization (i18n) friendly using the prefix attribute to change the accessible text inside the anchor links, e.g. <heading-anchors prefix="Ir a la sección titulada">
  • Default: Jump to section titled
• Use the content attribute to change the character used.
  • Default: #, supports an empty string if you want to use CSS pseudo elements.
• Style the anchor link using .ha-placeholder selector (change font-family, etc).
• Use the data-ha-exclude attribute to opt-out of an anchor link.

• https://github.com/daviddarnes/heading-anchors
• https://amberwilson.co.uk/blog/are-your-anchor-links-accessible/ (which has a lot of good related content too)

(Optional) There is a small layout shift by the addition of the # character. Add this CSS to make room for this pre-component definition:

heading-anchors:not(:defined) :is(h2,h3,h4,h5,h6):after {
	content: "#";
	padding: 0 .25em;
	opacity: 0;
}