We chose TypeScript at Codecov when undergoing a recent rewrite of a legacy front end. Our previous front end was a mishmash of vanilla JavaScript and CoffeeScript , and was expanded upon haphazardly as the need arose. Without a unifying set of paradigms and patterns, the CoffeeScript and JavaScript setup was proving hard to maintain and expand upon by an engineering team. During a move to Vue.js , we decided to also make the move to TypeScript. Integrating TypeScript and Vue.js is fairly well understood at this point, so the setup wasn't all that difficult, and we felt that the benefits of incorporating TypeScript would outweigh the required time to set it up and get our engineering team up to speed.

Choosing to add TypeScript has given us one more layer to rely on to help enforce code quality, good standards, and best practices within our engineering organization. One of the biggest benefits for us as an engineering team has been how well our IDEs and editors (e.g., Visual Studio Code ) integrate with and understand TypeScript . This allows developers to catch many more errors at development time instead of relying on run time. The end result is safer (from a type perspective) code and a more efficient coding experience that helps to catch and remove errors with less developer effort.