$ show microsoft/fast
This is the Microsoft FAST monorepo, a standards-based web component framework. It provides a lightweight, performant foundation for building custom elements with declarative templates, reactive data binding, server-side rendering (SSR), and hydration. The core library `@microsoft/fast-element` offers a complete runtime with observability, templating, dependency injection, and state management. Companion packages include a client-side router (`fast-router`), a test harness (`fast-test-harness`), and Rust-based build tools (`fast-build`, `fast-convert`) for SSR and template syntax conversion. The repository also contains example applications (CSR todo, SSR chat, WebUI todo), extensive Playwright integration tests, and a benchmark suite measuring rendering performance. The architecture is modular, with clear separation between runtime, build-time, and testing concerns. The codebase demonstrates high craftsmanship in areas like reactive observation, template compilation, hydration, and dependency injection, though some experimental features and cross-language (Rust/TypeScript) coordination introduce maintenance complexity.
The LLM identified 6 files worth highlighting for reuse:
A full-featured dependency injection container supporting singleton, transient, instance, callback, and alias registrations. Implements hierarchical containers, DOM-integrated context resolution, decorator-based injection (@inject, @singleton, @transient), and async resolution. The design is self-contained and could be extracted as a standalone DI library for any TypeScript project.
Core reactive observation system with property tracking, binding observers, volatile binding detection, and batched updates. Provides `Observable.defineProperty`, `Observable.binding`, `Observable.track`, and `Observable.notify`. This is a standalone reactive primitive that could be reused in any JavaScript project needing fine-grained reactivity without a full framework.
A route recognizer using a character-level state machine for matching static, dynamic, optional, and star segments. Supports parameter converters, name/path generation, and query-string parsing. The implementation is self-contained and could be extracted as a standalone URL pattern matching library.
A Playwright-based test fixture for client-side rendered web components. Provides `setTemplate`, `updateTemplate`, `applyTokens`, and `waitForCustomElement` methods. The abstraction encapsulates page setup, template rendering, and stability waits, making it reusable for any web component testing scenario.
A hand-rolled JSON parser in Rust that produces a `JsonValue` enum. Includes JavaScript-like truthiness evaluation and display string formatting. The parser is self-contained, has no external dependencies, and could be reused in any Rust project needing a minimal JSON parser.
Reactive state primitives: `state()` for shared state, `ownedState()` for per-owner state, and `computedState()` for derived values with setup/teardown. All return observable objects that integrate with the framework's binding system. These are reusable as a lightweight state management solution for any reactive UI.