I have been teaching JavaScript for many years. Between 2004 and 2011 I provided all the JavaScript pages for About.com. In 2011 I created http://javascriptexample.net which teaches introductory through intermediate JavaScript. I have also taught JavaScript classes at the local community college.
Stephen's article
How to Create and Manipulate Arrays in JavaScript
Learn how to create arrays in JavaScript, and how to manipulate them using their length property.