Author here! (neat, didn't think I'd see it submitted it here again, glad the person who dug this up found it useful!)
I made this four years ago as an experiment in D3 when the scroll-to-transition style was first getting popular (think nytimes and such).
All of it is basically hand-rolled D3 transitions with lots of debugging around enter/exit state... haven't looked at D3 lately so not sure if it's any easier. Charting libraries are a dime a dozen now, but these days when I need some easy charting, I like the D3+React bindings from VictoryCharts https://formidable.com/open-source/victory/docs/victory-char...
Kinda hard to wrap your head around how they do transitions in react-eese, but well, so is raw D3...
