The Javascript highlight isn't exactly surprising to me; I'd wager 100% of web developers have used Javascript at some point, with the vast majority of them using it frequently. This trend probably isn't tied to the surge in popularity of Node.JS (though that may be a contributing factor), seeing as virtually every web development project is using Javascript in their client side code.
It would be interesting if we could somehow separate front-end JS code from backend JS code to determine the relative popularity of (Node)JS among other backend languages like Java, PHP, C#, etc.