All in all, a great book! However, it left me even more confused about how JavaScript sets "this" than I was before. Fortunately, I found the discussion at http://stackoverflow.com/questions/3127429/javascript-this-keyword and the article at http://www.digital-web.com/articles/scope_in_javascript/ which both clarified open questions for me. But I am pretty sure I will forget JavaScript's context subtleties fairly quickly, and then I will have to look them up again. Oh well.
Crockford's approach is to focus on a subset of JavaScript which he considers sane, Of course there is much debate on what belongs into the subset and what doesn't. For example, Crockford bans the ++ and -- operators because they remind him too much of obfuscated C++ code. I did not find this particular advice too convincing, and it seems I am not alone.
To experiment with code from the book and test some code of my own, I used the jsc command-line JS interpreter on the Mac, and also toyed with http://jsfiddle.net/. (On Ubuntu, I guess I could have used rhino.)
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