I was sitting in a 'scoped' application context. ArrayUtil() was not available. I went to the 'Community' and found that all I needed to was to add 'global.' and the ArrayUtil() 'include' was available. Must admit that the course is quite informative. Fortunately, I have been dealing with C# for a few years (console utilities for work) and I could see the many similarities. My last 'touches' on JavaScript was way back in 2001/2003 for a class. Many thanks for the quite lively offerings. The focus on one or two things in each segment is great.