Mostly back end guys who have to do front end, and the genuine front end guys are indeed "ninjas" (though, I must say they are very good at wrangling JS and debugging the problems we inevitably run into). My boss is convinced at least, and I recently just convinced the team to move to proper testing + CI system (which the boss had wanted to do for 12 months but never had enough buy In from the team, so he was pretty stoked when I brought it up), so perhaps it'll just be a waiting game.
I'm tempted to reimplement a part of the system I'm currently working on in TypeScript to demonstrate it. I do worry that I'll come across as trying to show the team up though, as I'm still pretty new here :(
You're not going to get anywhere with the ninjas. Suggest a system that's similar to what you do your backend in. Is your backend in Java? Suggest Dart. Is your backend in C#? Suggest TypeScript. Is your backend in Ruby? Maybe you can at least get some CoffeeScript going.
I'm tempted to reimplement a part of the system I'm currently working on in TypeScript to demonstrate it. I do worry that I'll come across as trying to show the team up though, as I'm still pretty new here :(