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parcel-bundler/parcel
Parcel exposes production bundling and continuous development through both CLI and programmatic interfaces. The default configuration covers web languages, preprocessing tools, images, structured data, and specialized import pipelines. Development features include HTTP serving, HMR, proxy middleware, and execution of Node entry bundles. Separate utilities provide project scaffolding and an interactive browser build environment.
- serve starts development serving and supports lazy async bundles; watch rebuilds continuously; build exposes optimization, scope-hoisting, content-hash, and output-URL controls.
- The default transformer map handles JS/JSX/TypeScript, JSON/JSON5, YAML/TOML, GraphQL/GLSL, Sass/Less/Stylus, CSS, HTML/Pug, Vue, raster images, SVG, XML, and native Node assets; some implementations are installed on demand.
- Named pipelines support declaration generation, bundle-text and data-url imports, worklets, static React output, and URL assets; their packagers and optimizers can differ from ordinary file processing.
- TargetResolver filters package targets by requested names and rejects unknown targets; the default bundler groups entries by target and exposes shared-bundle size, request-count, and manual-bundle settings.
- Development serving includes HTML route fallback, source-file serving, configurable proxy middleware, and HMR updates; NodeRunner starts matching Node entry bundles in worker_threads and restarts them when HMR is disabled.
- CLI diagnostics render messages, code frames, stacks, hints, and documentation; users can add reporters, enable tracing or profiling, and trigger profiling or heap snapshots through terminal shortcuts.
- create-parcel copies a named template into an empty or new directory, initializes Git, installs dependencies with the invoking package manager, and creates an initial commit; the React client template supplies an editable App component.
- The REPL worker exposes bundle, watch, readiness, and service-worker coordination over Comlink; its Parcel instance uses an in-memory filesystem and returns bundle content, timing, optional graphs, and sourcemaps.