undom
1kb minimally viable DOM Document implementation
... undom lacks some DOM features like HTML parsing & serialization, Web Components, etc. These features can be added through additional libraries. One task undom doesn't handle for you by default is HTML serialization. A proper implementation of this would be cumbersome to maintain and would rely heavily on getters and setters, which limits browser support. Below is a simple recipe for serializing an undom Element (Document, etc) to HTML.