This was an error in the very first version of JavaScript. It was copied by Microsoft in JScript. They did an incredibly good job of reverse engineering Netscape's work. It's the most faithful copy Microsoft has ever made of anything, and probably the best and most diciplined engineering they've ever accomplished. The reason that we're here, talking about this language tonight, is because Microsoft did such a good job of finding and replicating ALL of the errors that were in the original JavaScript engine. When we got to ECMA, Microsoft then said, those errors are staying in the standard.

- Douglas Crockford