The main change in the new version of D3 is its use of “promises” (and the Fetch API) instead of asynchronous callbacks (via XMLHttpRequest) to load data. Fetch supports streaming responses that provide access to data as they become available to the application (rather than forcing waits until the entire dataset is generated).
The second major change is D3’s shift away from using twenty-color categorical color schemes (which risk suggesting false associations among groups of data) to using ColorBrewer to generate categorical, diverging, sequential single-hue, and sequential multi-hue schemes to represent both discrete and continuous data.
To begin, I think I’ll try my hand at visualizing data for mental health-related visits to emergency departments in Toronto. Stay tuned!