In order to improve my JavaScript skills, I used Marijn Haverbeke's textbook, "Eloquent JavaScript." This repository is a collection of the chapter-end exercises. I am using the NetBeans IDE (I am switching to NetBeans from Aptana Studio).
All relevant JS files are located in the public_html folder.
This is not an easy textbook to follow, but it has greatly improved my use of JavaScript higher-order functions and its object prototype system.
A free PDF of the textbook can be found here: http://eloquentjavascript.net/.