Javascript
Back in 2010, I argued about using javascript to rAun a node server (an option that was not popular at the time) because I wanted to learn one language to rule them all 🤟
Javascript seemed to be the cool kid in the corner that allowed me to write server, front, even AI.
So why not learn a language once and master it?
This absolutely paid off on the long term, even tho in some areas I do need to rely on other languages. The advent of tools such as typescript in react completely transformed the experience of writing code.