Adding a margin-top to a paragraph with a single bold string

Question

I have dozens of blog posts imported from a Wordpress site, where they have used single bold lines as headings (without tagging them as such). This is my content example:

<p><strong>This is a heading. I want to apply some CSS to this line of text</strong></p>
<p>But I don't want it applied here<strong>or here</strong> because this a paragraph.</p>

All I want is to apply a margin-top to those bold sentences to clarify that they are headings of a section.

I cannot modify the HTML (ie change them for H3) as it would mean going over all posts manually. I need to stick to CSS to make the change.

I have tried this and it was a pretty good solution. But it wasn't because the small paragraph in the example was being selected as well, as it only had one <strong> in it.

p:has(strong:only-child) {
    margin-top: 20px;
}

My thought was to find a way to EXCLUDE any <p> that had any "loose text" in it, apart of the single <strong> tag. But I don't know how to say "loose text" to use it in a :not() pseudo selector.

I want this rule to affect only this margin: Image

I hope it makes sense.

Answer 1

A better solution to your problem would be to query the database with a <p><strong> change using a regular expression.

If you still want to do it on the frontend, then you won't be able to do this with css.
I wrote one of the js solutions below. But I do not guarantee that it is perfect.

document.querySelectorAll('p').forEach(p => {
  // exclude empty <p> or <p> is not has <strong>
  if (!p.hasChildNodes() || !p.querySelector('strong')) { 
    return;
  }
  const childNodes = p.childNodes;
  // check whitespace
  if (childNodes[0].nodeType === Node.TEXT_NODE || childNodes[childNodes.length - 1].nodeType === Node.TEXT_NODE) {
    p.innerHTML = p.innerHTML.trim();
  }
  if (childNodes.length === 1 && p.childNodes[0].nodeName === 'STRONG' && p.childNodes[0].textContent.trim()) {
    p.style.marginBlockStart = '20px';
  }
})

* {
  margin: 0;
}

<p> <strong>This is a heading with whitespace</strong></p>
<p>But I don't want it applied here<strong>or here</strong> because this is a paragraph.</p>
<p><strong>This is a heading</strong></p>
<p>Lorem ipsum dolor sit amet.</p>
<p><strong></strong></p>
<p>Lorem ipsum dolor sit amet.</p>