TypeScript is an open source language, a superset of JavaScript. TypeScript compiler can transpile the code to various versions of ECMAScript, starting from ES3. This helps new features introduced in newer versions of ECMAScript to work in older browsers, without writing extra polyfills.
It brings new features such as:
TypeScript works well both in a browser and with Node.js. It is the default language in the Angular framework. We at Kiwee choose TypeScript for the majority of Javascript projects, because it increases productivity and code reliability.