This is forked from parse5 in order to support react-native.
The original README follows.
WHATWG HTML5 specification-compliant, fast and ready for production HTML parsing/serialization toolset for Node.js
parse5 provides nearly everything you may need when dealing with HTML. It's the fastest spec-compliant HTML parser for Node to date. It parses HTML the way the latest version of your browser does. It has proven itself reliable in such projects as jsdom, Angular2, Polymer and many more.