I wanted to raise two points about your explanation: First, while the function j is a closure, the anonymous function is not; it is simply a higher-order functi

I wanted to raise two points about your explanation: First, while the function j is a closure, the anonymous function is not; it is simply a higher-order function. Second, i is indeed undefined, but this will not cause a reference error, it will simply push undefined into the array. That's all :)