QuickJS JavaScript Engine

QuickJS is a free and open-source small and embeddable JavaScript engine that implements the ES2020 specification (and most of ES2023). Originally developed by Fabrice Bellard and Charlie Gordon at Bellard Industries starting in 2017 and first publicly released in 2019, QuickJS was designed as a compact, fast, and standards-compliant JavaScript engine suitable for embedding in applications, CLI tools, and resource-constrained environments. The quickjs-ng fork, maintained by the community since 2023, continues active development. Key features: ES2020+ compliance: implements the full ES2020 spec including modules, async/await, generators, proxies, symbols, BigInt, WeakRef, and structured cloning. Small footprint: the entire engine compiles to approximately 1.5 MB of x86-64 code, making it suitable for embedded systems and IoT devices. Fast interpreter: a compact bytecode interpreter with a custom register-based bytecode format. Bytecode is generated by a full compiler, enabling optimization passes. Fast startup: starts in under 1 millisecond, compared to V8's 20+ ms, making it ideal for short-lived scripts and CLI tools. Module system: full ES module support (import/export) with synchronous and asynchronous module loading. Standard library: implements JavaScript built-ins including Math, Date, RegExp, JSON, TypedArrays, and Atomics. Multi-threading: supports Worker threads for parallel JavaScript execution. REPL: built-in Read-Eval-Print Loop. Math extensions: supports bignum extension (arbitrary-precision arithmetic) and operator overloading. C API: clean embedding API for integrating JavaScript into host applications. Cross-platform: Linux, macOS, Windows, BSD. MIT.