mbostock/d3 — pull request #1649 by GoldyOrNugget (2013-11-24 04:08:37+00:00)
Title: Implement .size(), .empty() for d3.{set,map}

closes #1648.

I think ".empty()" is an ambiguous name. It could be taken to mean the action "empty this set/map" instead of the query "is this set/map empty?"