Closures exist, so what are they?
Closures are a style of writing JavaScript that provides object data privacy. What this seems to mean is that you can define a function within another function. Your child function will be able to access things from the parent function, but the parent function will not be able to access variables in the child function unless it explicitly calls the child function. The child function might also choose to return only a subset of data that it was provided. This is called partial application. ...