ECMA-262 Edition 3 is the latest ECMAScript standard. Edition 1 was based on my work at Netscape, combined with Microsoft's reverse-engineering of it (called JScript) in IE, along with a few other workalikes from Borland and a few other companies.
Were there any particularly hard/annoying problems you had to overcome in the development of the language?
Yes, mainly the incredibly short development cycle to prove the concept, after which the language design was frozen by necessity. I spent about ten days in May 1995 developing the interpreter, including the built-in objects except for the Date class (Ken Smith of Netscape helped write that by translating Java's java.util.Date class to C, unintentionally inheriting java.util.Date's Y2K bugs in the process!)
I spent the rest of 1995 embedding this engine in the Netscape browser and creating what has become known as the "DOM" (Document Object Model), specifically the "DOM level 0": APIs from JS to control windows, documents, forms, links, images, etc., and to respond to events and run code from timers.
I was the lone JS developer at Netscape until mid-1996.
We are seeing more games, both new and ported from other implementations, as well:
And John Resig's port of the Processing visualization language takes the cake.
And what's the worst?
I couldn't possibly pick one single worst JS program. I'll simply say that in the old days, JS was mainly used for annoyances such as pop-up windows, status bar scrolling text, etc. Good thing browsers such as Firefox evolved user controls, with sane defaults, for these pests. Netscape should have had such options in the first place.