TypeScript

TypeScript starts with the same syntax and semantics that millions of JavaScript developers know about. Use existing JavaScript code, include popular JavaScript libraries, and call TypeScript code from JavaScript. Types enable JavaScript developers to use high-performance development tools and techniques such as static validation and code refactoring when developing JavaScript applications. Types are optional, and type inference allows multiple type annotations to contribute greatly to static validation of your code. Types allow you to define interfaces between software components and get information about the behavior of existing JavaScript libraries.