O'Reilly has made a draft of the 6th edition of JavaScript: The Definitive Guide available through their Rough Cuts program. This means that you can buy online access (HTML and PDF) to the current draft of the book today, and then have the print version shipped to you when it is published, for the basic cover price of the book. (See the FAQ for more about how Rough Cuts works).
Online access is through Safari, not directly through O'Reilly, which means that you need to create an account with them in order to do this. But that's a minor hassle if you want the latest version right away.
Part I of the book is finished: complete coverage of ECMAScript 5, along with completely rewritten and modernized chapters on functions, objects and classes.
Part II is being updated for HTML 5 and is still in progress. The first few chapters have been pretty much completely rewritten but a number of chapters are still missing. The Rough Cuts edition will be updated each time I finish a new chapter. If you buy it now you get ongoing access to all the updates.
nice,
How much of html5 are you planning to cover?