feedExclude.js - Exclude content from 11ty feeds

feedExclude.js

/*

feedExclude.js - Exclude content from 11ty feeds

This filter replaces:

- any element with the "feed-exclude" class (recommended)
- any content found between <feed-exclude> tags

...with a link to the same post on the website.

Add as a filter to your 11ty content, then call the filter in your 
feed template with the URL of the post:

feedExclude(absolutePostUrl)

- You will need to add jsdom to your devDependencies
- Not tested with 11ty virtual templates
- Does not support nested <feed-exclude> tags

Post content:

  <p>Here is some content.</p>
  
  <p class="feed-exclude">Here is some content to be excluded.</p>
  
  <p>Here is some more content.</p>
  
  <feed-exclude>
    <p>Here is even more content to be excluded.</p>
  <feed-exclude>
  
 Feed output:
 
  <p>Here is some content.</p>
  <p>(<a href="https://example.com/url/to/post">Visit the website to see this content.</a>)</p>
  <p>Here is some more content.</p>
  <p>(<a href="https://example.com/url/to/post">Visit the website to see this content.</a>)</p>

*/

const { JSDOM } = require('jsdom');

module.exports = function(content, url) {
  const message = `(<a href="${url}">Visit the website to see this content.</a>)`;
  const dom = new JSDOM(content);
  const doc = dom.window.document;

  const elements = doc.querySelectorAll('.feed-exclude, feed-exclude');
  elements.forEach(el => {
    const p = doc.createElement('p');
    p.innerHTML = message;
    el.replaceWith(p);
  });

  return doc.body.innerHTML;
}