It looks pretty crappy.
Starting with with imperative programming sucks, see SICP lecture 5A for reasons.
It mixes concepts with irrelevant implementation details.
Why should students care about IEEE-754? Who gives a shit that you can use \n to get a newline and \t to get a tab in a string (and where are the rest of the escapes?). Does one really have to know how strings are ordered in Javascript? Perhaps the problem is the uncomfotable split between ``introduction to the JavaScript programming language and programming in general''.
That's just skimming Chapter 2.
I'm no teacher, but the writer obviously isn't either. He's just a shithead that finds it necessary to assault you with XKCD (
http://eloquentjavascript.net/chapter10.html#key6 ).