Our TypeScript development environment would not amount to much if we were not able to reuse the myriad of existing JavaScript libraries, frameworks, and general goodness that makes JavaScript development so popular today. As we have seen, however, in order to use a particular third-party library with TypeScript, we will first need a matching definition file.
Soon after TypeScript was released, Boris Yankov set up a GitHub repository to house TypeScript definition files for third-party JavaScript libraries. This repository, named DefinitelyTyped (https://github.com/borisyankov/DefinitelyTyped), quickly became very popular, and is currently the place to go for high-quality definition files. DefinitelyTyped currently has over 5,000 definition files, built up over time from hundreds of contributors from all over the world.
If we were to measure the success of...