the possible value of _hull[code] that must be considered are or are TRUE, FALSE, undefined, NULL,
FALSE is unexpectedly not possible in practise ... in the PR the condition is restricted by the possible return type of .has() to true/false and so it much safer to handle/ reason with
I have given a detailed explanation in
https://github.com/Fil/d3-geo-voronoi/issues/23
Here is the PR .. in short
When visually inspecting this if statement
if (_hull[code]) delete _hull[code];
the possible value of _hull[code] that must be considered are or are TRUE, FALSE, undefined, NULL,
FALSE is unexpectedly not possible in practise ... in the PR the condition is restricted by the possible return type of .has() to true/false and so it much safer to handle/ reason with