Intention Hidden In Implementation And Misty Edge of Validity

“The code is the documentation” – except that from poorly written code you cannot tell what is an intrinsic part of the solution and what is an accidental implementation detail. And a piece of code can rarely handle any possible data – yet, without a good documentation or precondition checks, you can’t even guess at what are valid or unexpected inputs. Today we will explore a piece of JavaScript code that both hides the intention in the implementation (the “why” is not clear from the “what” the code does) and operates correctly only under particular but unstated conditions.