> IMO the biggest tragedy is Mozilla's unwillingness to put other languages in the browser. Dart was developed in public, far more of an open standard than the original JS, fixed language design problems that ES6 still isn't addressing, had an adequate approach to running in JS-only browsers, and would have added much less complexity to browser implementation (the reason given for rejection) than many standards that Mozilla has been happy to support.

It's also Google's failure to exploit their market position. Instead of using Dartium, they should've just integrated the Dart VM into mainline Chrome and began paying web developers to use Dart. Mozilla would then have no choice but to implement Dart or find their users complaining about not being able to access their favorite websites.

On a similar note, it's kind of a shame that IE's support for VBScript never took off. Not because VBScript was a good language, but because it would've laid down a precedent for the web being a multi-language environment. Browser vendors would have developed pluggable scripting architectures to compete. Imagine if, say, every browser on Windows could have allow scripts written in, for example, everything offered by Windows Script Host (and I'm sure some equivalent architecture would have been developed for Mac and Linux -- maybe even something as simple as "any script that can be interpreted via a shebang line").