@xmldom/xmldom

@xmldom/xmldom is a dependency-free JavaScript implementation of the DOM Level 2 Core API, providing DOMParser and XMLSerializer classes that work identically in Node.js and browsers. It exists to fill the gap left by document.implementation not being available server-side, giving Node code (and any environment lacking a native DOM) a spec-compliant way to parse XML/HTML strings into a traversable DOM tree and serialize a tree back to a string.

What You Get

• A DOMParser class with parseFromString() that turns an XML or HTML string into a standards-compliant DOM Document
• An XMLSerializer class that turns a DOM tree back into a string, mirroring the browser API
• A hand-written SAX-style tokenizer (lib/sax.js) and grammar module underpinning the parser, with no native bindings or WASM to install
• Configurable error/warning handling via onError callbacks so malformed input can be caught instead of silently producing a broken tree

Common Use Cases

• Parsing XML config files, SOAP responses, RSS/Atom feeds, or SVG documents in a Node.js backend with no DOM available
• Server-side rendering or testing code that expects browser DOM APIs (DOMParser/XMLSerializer) but runs outside a browser
• Feeding parsed documents into XPath libraries (e.g. xpath) that expect a DOM Level 2 tree to query against
• Manipulating and re-serializing HTML/XML documents in build tools, static site generators, or CLI utilities

Under The Hood

Architecture The library is organized around a small set of focused modules: sax.js implements a hand-rolled streaming tokenizer that walks the input string and emits parse events; dom-parser.js consumes those events to build up a DOM tree using the Document/Node/Element classes defined in the large dom.js (3,500+ lines implementing DOM Level 2 Core); entities.js handles the full HTML/XML named-entity decoding table; and errors.js/conventions.js centralize error typing and shared helpers. There is no external parsing dependency — the tokenizer, grammar, and DOM implementation are all original code. Tech Stack Pure JavaScript (CommonJS, lib/index.js as the entry point) with hand-authored TypeScript declarations (index.d.ts) shipped alongside rather than generated from source; zero runtime dependencies keep the install footprint small, and the dev toolchain uses Jest for testing, ESLint/Prettier for style, and auto-changelog for release notes. Code Quality The test suite is substantial — 64+ test files under test/ covering dom, dom-parser, entities, errors, grammar, HTML parsing, and dedicated conformance/parse suites, plus a jest.fuzz.config.js for fuzz testing malformed input, which is unusually thorough for a parser library and reflects real-world hardening against XML edge cases (external entities, malformed tags, encoding quirks). API Design The public API deliberately mirrors the browser’s native DOMParser/XMLSerializer interfaces, so code written against real browser DOM parsing can often switch to this package with a single import change and no rewrites; the tradeoff is that advanced configuration (custom error handling, MIME type selection) requires reaching for slightly less-discoverable constructor options rather than a fluent builder API.