[softyeti]

I believe you may not have addressed what your tech lead is worried about. He/She has to make sure that everyone can do what you are trying to do from an architectural standpoint if you are all going to build upon it.

You are outlining the benefits, but JavaScript is very different from other languages and can be hard to understand, let alone master all of the libraries based on it.

If you can address those issues, then you may be able to convince your lead.

I've been on both sides of the coin here. When deciding on a platform or language, I usually choose what is going to be the easiest to use, or what has a high adoption rate which will provide the documentation and Q&A information online.