JS++

JS++ is a proprietary programming language for web development that extends JavaScript with a sound type system. It includes imperative, object-oriented, functional, and generic programming features.

History
JS++ first appeared on October 8, 2011. The modern implementation was announced at DeveloperWeek 2016 and released on May 31, 2016. The language is designed by Roger Poon and Anton Rapetov.

Type annotations
Since JS++ is a superset of JavaScript, declaring types for variables is optional.

Features
JS++ features a type system that is sound.

JS++ is able to efficiently analyze out-of-bounds errors at compile time.

Compiler
The JS++ compiler is available for Windows, Mac OS X, and Linux. The compiler generates JavaScript output.

Editor integration
JS++ integrates with various code editors including Visual Studio Code, Atom, and Sublime Text.

Build tools
JS++ can be integrated with third-party build tools like Webpack.