Clone the repository, and open spec/index.html in a modern browser.
You may need to start a local http server instead of opening off the file
system. If you need an http server, npm install -g http-server works great.
The document format for the specification uses Custom Elements and Imports. The custom elements give semantic meaning to ECMAScript constructs and keep markup terse. Imports enable breaking the specification up into many files while avoiding a build step. Everything is plaintext and can be edited with any tool.
The html files were generated from html produced by Jason Orendorf's
es-spec tool. The script
tasks/parse.js parses the html input and builds the output html under
the spec directory. Currently this process introduces some bugs but once
the document format is deemed stable the parser can be jettisoned and
one-off markup issues fixed manually.