Adopt type: module. #3501
Adopt InternMap for ordinal scale domains.
d3.ascending and d3.descending no longer consider null comparable.
d3.bin now ignores nulls.
Convert array-likes (e.g., live NodeList) to arrays in d3.selectAll and selection.selectAll.

Non-breaking changes:

Add d3.mode.
Add d3.flatGroup and d3.flatRollup.
Add transition.selectChild.
Add transition.selectChildren.
Adopt robust predicates for Delaunay triangulation.
Fix delaunay.voronoi’s computed circumcenters for collinear points on the hull.
Allow brush.move and brush.clear to take an optional event.
Allow selection.merge to take a transition.
Allow selection.join to take transitions.
Apply linear binning for d3.contourDensity.
Generate contours.thresholds at nicer round tick values.
Fix axis.tickArguments to accept an iterable.
Fix axis.tickValues to accept an iterable.
Fix undefined event during brush.move.
Fix drag event listeners to be explicitly non-passive where necessary (#78).
Fix zoom event listeners to be explicitly non-passive where necessary.
Fix variable initialization error in d3-zoom.
Expose d3.ZoomTransform constructor.
Update dependencies.
Make build reproducible.

D3 now requires Node.js 12 or higher. For more, please read Sindre Sorhus’s FAQ.