Prepack is a build-time code evaluator and JavaScript bundle optimizer. It functions as a static analysis compiler that pre-evaluates static code and precalculates function results and global assignments during the build phase to accelerate startup times and reduce bundle size.
The project specifically targets JSX optimization by processing syntax and node serialization to improve user interface rendering efficiency. It utilizes a partial evaluation engine and static execution analysis to replace runtime computations with precalculated constants.
The tool covers a range of capabilities including the removal of TypeScript type annotations, the inlining of single-use expressions, and the simulation of environment-specific globals. It integrates into frontend build pipelines and can be operated via a command-line interface.