Google Closure Compiler vs Rslib

Google Closure Compiler optimizes JavaScript by analyzing code, removing dead code, and rewriting and minimizing what remains. It can also check syntax, references, and types, and warn about illegal JavaScript, risky operations, and common pitfalls. Google says smaller output files can help applications load faster and reduce bandwidth needs. Compilation options include WHITESPACE_ONLY, SIMPLE, and ADVANCED; the repository README also lists BUNDLE. ADVANCED applies aggressive transformations and symbol renaming to improve compression, so preserving program behavior requires care. The project is available as a command-line Java application, a library used through Bazel, and an NPM package. Released JARs are distributed through Maven. The repository documents Maven, NPM, Bazel, command-line Java, and a NodeJS API. Building the compiler requires Java 21 or later, NodeJS, Git, and Bazelisk. Its input restrictions include use of goog.module() and goog.require(), and ES6 import/export support is not actively maintained. The NPM packages are built and distributed by an open source contributor, not Google. The compiler is free.

Rslib is a free, open-source tool for developing JavaScript packages and UI component libraries. Based on Rsbuild and powered by Rspack, it integrates Rust-based tools including SWC and Lightning CSS. It supports bundle and bundleless build modes and outputs ESM, CJS, UMD, Module Federation, and IIFE formats. Framework integrations support component libraries for React, Vue, Svelte, and Solid. Rslib can generate TypeScript declaration files, including isolated declarations, though declaration generation is not enabled by default. Plugin support includes Rsbuild, Rspack, and webpack plugins. Its development integrations include Rstest for testing, Storybook for component development, Rspress for documentation and component previews, and Rsdoctor for build analysis. The quick-start guide lists Node.js, Deno, and Bun as runtime options, while Rslib v1 requires Node.js 20.19+ or 22.12+. It is available for API, Linux, macOS, web, and Windows, and is released under the MIT license.