How did JavaScript compilers work?

JavaScript compilers, such as the one used in Clang, involve complex processes to translate code effectively. The compiler design can be challenging, often involving the management of global variables and reusability issues. Clang, for instance, emphasizes a better user interface, improving error messages compared to GCC, and enhancing compile times. This is achieved while maintaining efficient bookkeeping of additional information required during the compilation process.

The process also includes creating refactoring tools and other analysis tools, a feature traditionally not supported by GCC. Leveraging the extra information maintained enables these advanced tools, integrating them into IDEs for better development experience. The compilation process includes multiple stages such as parsing the code into an Abstract Syntax Tree (AST), where each part like function calls or operations is turned into nodes. This AST then undergoes transformation in a series of roughly 150 different passes, organized in complex ways to influence the compiled code's performance and efficiency 1 .