Ordinarily I'm a BIG fan of Wrox books, but this one let me down. Like many other reviewers, I was stopped too often by poor grammar, unintelligible sentences, and just plain wrong information. That this book ever made it to publication is an indictment of the Wrox editorial staff. Don't buy the book if you want to understand Javascript. In fact, don't buy it at all. I'm returning my copy (if I can).