A JavaScript rich text editor that stores blocks (paragraphs, images, etc.) in a structured way. Each block is an entry in a JSON list. Paragraphs contain HTML inline.It seems a bit strange to me to mix JSON with HTML given that HTML itself is a mark-up language for semi-structured data.
Embedding it in XML as a dialect would have felt more natural to me. Such an arrangement would have been especially useful when the desired output format is not HTML, but, say, TeX or Markdown.