$ cloc --version
1.82
$ cd /path/to/mediawiki
$ cloc --include-ext js,less,css extensions/MobileFrontend/{includes,src,resources,tests}
     413 text files.
     412 unique files.                                          
     163 files ignored.

github.com/AlDanial/cloc v 1.82  T=0.36 s (691.3 files/s, 66779.0 lines/s)
-------------------------------------------------------------------------------
Language                     files          blank        comment           code
-------------------------------------------------------------------------------
JavaScript                     208           1872           5388          14324
LESS                            43            392            363           1909
-------------------------------------------------------------------------------
SUM:                           251           2264           5751          16233
-------------------------------------------------------------------------------