[malandrew]

"You must master is now." Most certainly true. If not for production, you will at least use if d for communication of your work on the Internet.

"JavaScript is making all other languages irrelevant" Hogwash. Many many languages out there have something to offer you intellectually and professionally. Saying they are all now irrelevant is naïve and the path to mediocrity.

[anonyfox]

For intellectual fun and profit, there is an increasing number of "meta"-languages out there which compile to javascript. See Coffeescript and Livescript for Example.