People usually get hired to use a particular primary language (though even then, I've worked in jobs where I was hired for Java that ended up switching to Scala mainly due to developer preference), but often have broad discretion over which languages to use for secondary tasks. Certainly in a lot of "Java shops" the pattern I've seen is that devs will not be second-guessed (or at least, will contribute to team consensus) in their choice of bash/python/ruby/scala/... for things like testing scripts or data migration tools, nor in their choice of coffeescript/typescript/... for frontend parts.