I would go with O'reilly's JavaScript: The Definitive Guide, (5th ed) (aka The Rhino book, ISBN 9780596101992).
It aims at all levels, so it does have sections about what are variables, and loops and regexes and suchlike, but so do Programming Perl, and the K&R, and similar to those, it's the most comprehensive and correct reference material I'm familiar with regarding JS.
I'm going to go with my usual recommendation regarding learning a language, and that is to create a project in it, with one hand on the book for reference. It usually helps you get along faster than cover-to-covering the book.

I don't even know if Javascript supports closures

It does. JavaScript's strongest point is what I like to call "Everything is Everything", meaning that almost every element in the language (functions, arrays, objects, assoc. arrays, variables, numbers, regexes) can be used, or assigned as any other, with very powerful results. The language was design to exist solely in a browser, giving it a sort of "sandbox" design where you can just go nuts with your syntax and achieve complex and powerful results (Similar to Emacs-LISP, if you're familiar with it).
In this type of landscape, functions can be declared as variables, Objects, be interpreted as arrays/assoc. arrays and do some other things, which suggests a very strong "functional" methodology. JS is also very OO, although prototype-based, which goes very handy with the DOM structure it functions in. Its data-format, JSON, comes from the language itself, so no added tools are needed to read/write it. I find it to be very fun and cute language, if only it wasn't so inadequately and incompatibly implemented by different client-software.