JSON feed template for eleventy-plugin-rss

.eleventyconfig.js

const pluginRss    = require("@11ty/eleventy-plugin-rss");

module.exports = function(eleventyConfig) {

  // Lots of other stuff probably goes here
  
eleventyConfig.addCollection("allUpdates", function(collection) {
    return collection.getFilteredByGlob(["posts/*.md", "photos/*.md", "notes/*.md"]).sort(function(a, b) {
      return b.date - a.date;
    });
  });
  
  // Lots of other stuff probably goes here
  
}

jsonfeed.njk

---
permalink: feed.json
metadata:
  title: My Site Title
  url: https://my.url
  author:
    name: My Name
    email: me@my.url
    avatar: /path/to/pic.jpg
  feed:
    subtitle: My feed subtitle
    filename: feed.json
    path: feed/feed.json
    url: https://my.url/feed.json
    id: https://my.url
---
{
  "version": "https://jsonfeed.org/version/1",
  "title": "{{ metadata.title }}",
  "home_page_url": "{{ metadata.url }}",
  "feed_url": "{{ metadata.url }}/feed.json",
  "favicon": "{{ metadata.url }}/static/img/icon.png",
  "icon": "{{ metadata.url }}/static/img/icon.png",
  "description": "{{ metadata.feed.subtitle }}",
  "author": {
    "name": "{{ metadata.author.name }}",
    "url": "{{ metadata.url }}",
    "avatar": "{{ metadata.url }}{{ metadata.author.avatar }}"
  },
  "items": [
    {% set comma = joiner(",") -%}
    {%- for post in collections.allUpdates -%}

      {%- set absolutePostUrl -%}{{ post.url | url | absoluteUrl(metadata.url) }}{%- endset -%}
      {%- set title -%}{{ post.data.title }}{%- endset -%}
      {%- set banner -%}{{ post.data.hero.image }}{%- endset -%}
      {%- set summary -%}{{ post.data.summary }}{%- endset -%}
      {%- set heroimg -%}{{ post.data.hero.image }}{%- endset -%}
      {%- set herocap -%}{{ post.data.hero.caption }}{%- endset -%}

      {%- set reg1 = "\"" -%}
      {%- set rep1 %}\"{% endset -%}
      {%- set reg2 = "\\\\\\" -%} {# Handling one weird edge case! #}
      {%- set rep2 %}\\\\\\{% endset -%}
      {%- set reg3 = "\n" -%}
      {%- set rep3 %}\n{% endset -%}
      {%- set reg4 = "\r" -%}
      {%- set rep4 %}\r{% endset -%}
      {%- set reg5 = "\t" -%}
      {%- set rep5 %}\t{% endset -%}

      {{- comma() }}
      { "id": "{{ absolutePostUrl }}",
        "content_html": "{%- if heroimg -%}<figure><img src=\"{{ heroimg | url | absoluteUrl(metadata.url) }}\" alt=\"{{ herocap }}\"><figcaption>{{ herocap }}</figcaption></figure>{%- endif -%}{{- post.templateContent
             | htmlToAbsoluteUrls(absolutePostUrl)
             | replace(reg1, rep1)
             | replace(reg2, rep2)
             | replace(reg3, rep3)
             | replace(reg4, rep4)
             | replace(reg5, rep5)
             | safe -}}",
        "url": "{{ absolutePostUrl }}",
        "date_published": "{{ post.date | rfc3339 }}"
        {%- if summary %},
          "summary": "{{ post.data.summary }}"
        {% endif -%}

        {%- if not "note" in post.data.tags %},
          "title": "{{ title }}"
        {% endif -%}

        {%- if banner %},
          "banner_image": "{{ metadata.url }}{{ banner }}"
        {% endif -%},
        "author": {
         "name": " {{ metadata.author.name }}",
         "url": "{{ metadata.url }}",
             "avatar": "{{ metadata.author.avatar | url | absoluteUrl(metadata.url) }}"
 },
      }
    {% endfor %}
  ]
}