Log4js seems to have support for hierarchies of loggers by using the '.' character as separator:
#392 (comment)
5283782#diff-563911440c8b98daa0ca68f53193a251R47 (although it seems that even before this was somewhat working due to prefix matching?)

I cannot find any documentation that spells out this support, and unfortunately there is also an older issue which seems to indicate that no such support exist: #193 (comment).

It would be great to have this documented to help future googlers :)