You can now pass custom element constructors as the node name of a virtual element. This was implemented at the diff level so that it could efficiently, and correctly, check based on constructors as opposed to somehow determining the node name and reusing the existing algorithms. This is both more efficient than the aforementioned and spec compliant.

- No destructuring
- No lowercase() function, use .toLowerCase() instead
- Favour property access (no variable saving, unless necessary)
- Use `'nodeName' in vnodeName.prototype` instead of HTMLElement instance checking