Simple Pie Chart:
A vanilla HTML implementation of a reusable version of tutorials teacher V5 example (https://www.tutorialsteacher.com/d3js/create-pie-chart-using-d3js).
The reusable chart is derived from Mike Bostock's Towards Reusable Charts (https://bost.ocks.org/mike/chart/) as the source of the foundational principles. But uses the ProD3 pattern (Pro D3.js Use D3.js to Create Maintainable, Modular, and Testable Charts by Marcos Iglesias https://www.apress.com/gp/book/9781484252024) as the basis for the charts.
Addtional help from and aknowledgement to: