Prepack
A JavaScript bundle optimizer
... and object allocations. Prepack operates at the AST level, using Babel to parse and generate JavaScript source code. At the core of Prepack is an almost ECMAScript 5 compatible interpreter — implemented in JavaScript! The interpreter closely follows the ECMAScript 2016 Language Specification, with a focus on correctness and spec conformance. You can think of the interpreter in Prepack as a clean reference implementation of JavaScript.