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How to automatically add unique ID’s to H2 tags for content deep-linking

Learn how to add direct links to H2 so that you can point to specific parts of your articles.

In general, for most of my blog posts, I have the following structure:

<h1>Main topic of the post</h1>
    <h2>Subtopic 1</h2>
    <h2>Subtopic 2</h2>
    <h2>Subtopic 3</h2>

I've needed a way to point to a specific h2. For anchors, you can do that by pointing to a URL followed by the ID of an element from the page:

<h2 id="anchor-name">The title where you want to jump</h2>
<a href="">
    Jump to the part of the page with the ID of “anchor-name”  

The whole idea was to be able to do this without manually adding ID's to each secondary title I have on each page.

Initially, I tried to make this somehow with a combination of CSS counters and maybe the content property of before and/or after pseudo-classes.

When that solution failed, I've ended up with the below JS script:

document.querySelectorAll(' h2').forEach(h => {
  //create id from heading text
  var id =
    h.getAttribute('id') ||
      .replace(/[`~!@#$%^&*()_|+\-=?;:'",.<>\{\}\[\]\\\/]/gi, '')
      .replace(/ +/g, '-')

  //add the id to the heading
  h.setAttribute('id', id)

  //append parent class to heading

  //create an anchor
  let anchor = document.createElement('a')
  anchor.className = 'anchor-link'
  anchor.href = '#' + id
  anchor.innerText = ' #'

  //append anchor after heading text

What the script does is to pick all the h2 elements we have on the page. If that element does not yet has an ID attribute give it one made from the words of that title separated by a dash character. And at the end appends a # character so that we can easily point to it.

For example, checkout this link that points directly to why should I use HSL colors over other formats such as RGB or Hexa.

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