When it comes to more traditional languages like C, C++ and Java, "fully fledged" and "big scale" are descriptors usually reserved for multi-million line systems consistently worked on by 50+ full-time developers at a time.
I'm very suspicious of such terminology being applied to JavaScript applications. We generally see a much, much smaller scale when it comes to those. The "high end" cases are usually topping out at 100,000 to 200,000 lines of code at most, and perhaps 10 or 20 developers. They're a far cry from the C, C++, Java and C# examples.
Is any of this code you've worked on publicly available?
In most of my limited experience JS has been harder to work with than almost anything I have encountered. My personal experience using JS client side apps has left me feeling sour. Every time I visit a webpage and immediately hit a JS loading screen I cringe. Gmail is about the only I dont completely dislike that I know is written in JS.