tiptap/packages/core/src/helpers/getHTMLFromFragment.ts

import { DOMSerializer, Schema, Fragment } from 'prosemirror-model'

export default function getHTMLFromFragment(fragment: Fragment, schema: Schema): string {
  const documentFragment = DOMSerializer
    .fromSchema(schema)
    .serializeFragment(fragment)

  const temporaryDocument = document.implementation.createHTMLDocument()
  const container = temporaryDocument.createElement('div')

  container.appendChild(documentFragment)

  return container.innerHTML
}