DefinitelyTyped

Soon after TypeScript was released, Boris Yankov started a GitHub repository to house definition files, called DefinitelyTyped (http://definitelytyped.org) . This repository has now become the first port of call for integrating external libraries into TypeScript, and it currently holds definitions for over 1,600 JavaScript Libraries. The growth of this site, and the rate at which type definitions have been generated for many JavaScript libraries, shows the popularity of TypeScript.