jsdiff is a mature, zero-dependency JavaScript/TypeScript library for computing text differences and manipulating unified diff patches. In production it serves as the diffing engine for code review tools, editors, and version-control tooling: it computes character-, word-, line-, sentence-, CSS-token-, and JSON-level differences between two inputs using Myers' O(ND) algorithm, and can generate, parse, apply, and reverse unified diff patches including Git-style patches with rename/copy/create/delete metadata. The architecture is a clean library design built around an extensible base Diff class (src/diff/base.ts) that implements the core algorithm and delegates tokenization, equality checking, and output joining to subclasses; each diff variant is a thin specialization. The patch subsystem (create/parse/apply/reverse) is cleanly separated from the diff core, and converters emit Google diff-match-patch and XML formats. The public API is exported from src/index.ts with extensive TypeScript overloads supporting synchronous, callback-based asynchronous, and abortable (timeout/maxEditLength) modes. The library ships ESM, CommonJS, and UMD browser bundles and has essentially no runtime dependencies beyond platform APIs like Intl.Segmenter. The project is actively maintained with regular releases and a history of security and performance fixes (ReDoS, O(nĀ³) worst-case behavior). The test suite is extensive, covering Unicode code points, line-ending variations, no-newline-at-EOF markers, malformed patch inputs, and includes dedicated TypeScript type tests (test-d/). Known limitations include formatPatch/parsePatch not being strict inverses for all formatting variations, and Intl.Segmenter-based word tokenization varying across environments. Overall this is a high-craftsmanship library with a large but well-documented API surface.