Agreed, but just wanted to add the context that you get undefined values by trying to access uninitialised things such as out of bounds array elements, get on a

Agreed, but just wanted to add the context that you get undefined values by trying to access uninitialised things such as out of bounds array elements, get on a map-like object with a key that's yet to be set, unset properties on a object, return value of a function that returns void, etc.