mbostock/d3 — pull request #2077 by martoranod (2014-10-18 03:51:46+00:00)
Title: Add better handling for returning undefined.

Appends an undef function that returns _nothing_ (undefined) to `d3` and updates instances of code that return undefined with `d3.undef()` to prevent from undefined re-assigning bugs. Arguably not quite useful, but also defensible that large projects such as this, present a higher than trivial probability to incur in bugs of this nature.

Best.
D