As a React test project, this bl.ock was converted into React components for Boulder's D3js Meetup.
https://d3js.org/d3.v5.min.js
https://cdnjs.cloudflare.com/ajax/libs/d3-annotation/2.3.1/d3-annotation.independent.js
https://cdnjs.cloudflare.com/ajax/libs/d3-annotation/2.3.1/d3-annotation.js
https://cdnjs.cloudflare.com/ajax/libs/d3-legend/2.25.6/d3-legend.js