Richtext renderer with custom schema to add classes directly to headlines

RichtextRenderer.js

const RichTextResolver = require('storyblok-js-client/dist/richTextResolver')
const MySchema = require('storyblok-js-client/dist/schema')

MySchema.nodes.heading = function(node) {
  let attrs = {}

  if (node.content &&
      node.content.length === 1 &&
      node.content[0].marks &&
      node.content[0].marks.length === 1 &&
      node.content[0].marks[0].type === 'styled') {
    attrs = node.content[0].marks[0].attrs
    delete node.content[0].marks
  }

  return {
    tag: [{
      tag: `h${node.attrs.level}`,
      attrs: attrs
    }]
  }
}

let rteResolver = new RichTextResolver(MySchema)
let rendered = rteResolver.render({
  "content": [
    {
      "content": [
        {
          "text": "Normal headline",
          "type": "text"
        }
      ],
      "type": "paragraph"
    },
    {
      "attrs": {
        "level": 3
      },
      "content": [
        {
          "marks": [
            {
              "attrs": {
                "class": "margin-bottom-fdsafdsada"
              },
              "type": "styled"
            }
          ],
          "text": "Styled headline",
          "type": "text"
        }
      ],
      "type": "heading"
    }
  ],
  "type": "doc"
})

console.log(rendered)
// Returns <p>Normal headline</p><h3 class="margin-bottom-fdsafdsada">Styled headline</h3> instead of <p>Normal headline</p><h3><span class="margin-bottom-fdsafdsada">Styled headline</span></h3>