explain some of the quirks about things being undefined

[smcalilly]

I keep having this problem when I try to play around with getting "Undefined". I created my own repl and tried to recreate the Array example and I get undefined. Why is this happening? Need to make this clear whatever code I need to have first so I can copy and paste your examples. Same thing happened in my browser console when I tried to copy / paste the "sayHello" example.

I guess I'm expecting it to work like a Ruby console where I can define a method in the console and then use it in the same console session. Do I have to save the function into a file in the Repl to then be able to use it? Is it possible to make the repl examples interactive in this way where the reader does the typing? Clicking "Run" on your code really doesn't help me learn.