Time in web applications is not used looking up array lengths - it's used in IO, layout, and DOM manipulation. If iterating through arrays was found to ever be

Time in web applications is not used looking up array lengths - it's used in IO, layout, and DOM manipulation. If iterating through arrays was found to ever be a noticeable issue in practice, the Closure compiler could just be modified to emit more efficient code. That's one of the advantages of having the compiler - you don't have to make a convenience/readability trade. Closure was not thrown together by novices new to the language. It was started by Erik Arvidsson and Dan Pupius, two JS hackers that have been doing this kind of work longer than just about anyone else. Its differences from other libraries aren't the result of ignorance, they're mostly the result of conscious tradeoffs to make compilation more effective. Edit: Oh, and the string thing... If you ever do new String("foo") in JavaScript, you're doing it wrong.