Typescript

Snippet of the Wikipedia Definition that captures Typescript well:

TypeScript is a free and open source programming language developed and maintained by Microsoft. It is a strict syntactical superset of JavaScript and adds optional static typing to the language. It is designed for the development of large applications and transpiles to JavaScript. As it is a superset of JavaScript, existing JavaScript programs are also valid TypeScript programs.

Typescripts 1.0 release was in 2014, so it's a relatively young language. Though it is already in widespread use, especially in the professional world.