This is mostly for tactical reasons. It's hard to
get 100% test coverage on topic_list.js, but it
should be easy to get 100% test coverage on this
very important function.
I considered just moving this code into topic_data.js,
but it just didn't feel quite right. I feel like
this is a pretty core piece of code that's nice
to be by itself and not be near other complicated
code that does stuff like build widgets or talk
to servers. (And, again, it's not just the actual
code here, which is pretty small, it's the unit
tests, which are inherently verbose to exercise
all the edge cases.)
Steve Howell