Javascript is a very obvious decision in a modern (frontend-)world. We try to utilize functional programming patterns as much as possible, while leveraging modern libraries wherever we can. On the backend we have partially node. On the frontend we have basically everything in javascript, from tooling, to jsx, react and styling. This creates a very homogenous frontend-stack, where every developer can understand and write everything.

The drawbacks of this decision are some learning curves when it comes to styling things in js.