I don't want to pile on but that sentence strongly reminded me of the oldish saw about "a data scientist is a programmer who lives in SF". I've never heard of anyone using JS for data science. What might it have that's anywhere comparable to the tidyverse or numpy/scipy/sklearn?
They don't use JS to investigate the data, they use SQL (Hive, Impala etc.) as their lingua franca for exploring datasets. But they then write their algorithms based on that analysis in JS.
Again, I don't know why, it struck me as odd also, but hey, whatever they're doing, it works for them.