The Google Closing Compiler Is a JavaScript Script Composer

The Google closure script compiler can normally be used as you download the jar. It's like an executable to our one of those that you can run from the command line. And then at the very end if you are doing an advanced build it then calls the Google closure compilation which produces optimized JavaScript. So when you want to contribute actually to the compilers you should also be familiar or when you should be familiar with the Google closure.