Let me post a small update on how things are progressing.
I am taking my time during the JavaScript migration. While initially I planned just for the simple code refactoring, I decided it’s much more sensible to write the functionalities from scratch, while preserving the same behavior. I am super happy about the current state of the JavaScript code. There are numerous optimization, bug fixes, simplifications, and other improvements (too much to talk about right now). I will describe everything in rich detail on the test server launch - which is my primary focus right now 
. I can see a light at the end of this tunnel.
Here’s a small sneak peek at one of the cool new features (as a thank you for reading this post):
In OpenStreetMap-NG, image map export (from the share menu) is done client-side instead of the server-side. This has numerous advantages: it allows users to export any base layer and not just mapnik, is much faster as the client browser can reuse tile cache, can be easily extended in the future, eases out OSM server maintenance and reduces cost, and has a new very intuitive user interface. 