Well, you need to use javascript if you want it to run in a browser.  So 
that's one reason to pick it, and the main reason people pick it for 
it's most popular uses.

It will be very difficult to get javascript running in a browser to do 
what you just said though. Not sure if you were running your js in an 
arbitrary client's browser, or server-side.

You _can_ run javascript server-side, but it requires setting up a JS 
interpreter of some kind, etc., and most people don't do it just for the 
heck of it, they do it because they have some specific reason to want 
javascript for that. They want to be on the cutting edge trying out 
crazy new things, they just love javascript, they particularly want the 
non-blocking functionality of the node.js server, they need to interact 
with other libraries of functions already written in js, they have some 
crazy plan to share code between server-side and client-side, etc.

So, yeah, I think you were on the right track, I'm not sure why you were 
trying to do that in javascript either!