> True, but the JS VMs we have today have been refined over 15+ years and switching to another risks breaking the web in profound ways. Even Google would be against dropping V8 for JS use.

And yet, Google, Apple, AND Mozilla have all successfully introduced entirely new or significantly refactored VMs in the past few years.

This is solvable; it HAS been solved.

> JavaScript still has a lot of room for improvement. Putting resources in an alternative (whatever shape that might take) distracts from improving JavaScript.

This doesn't seem contrary to what I've stated above; it's an argument in favor of JavaScript over investing in a generic VM that would open up the ability to develop new browser languages to everyone.

In that regard, failing to allow others to implement custom/experimental languages seems counterproductive to the ultimate goals you seem to be stating here.

> For those who have a general syntax/style problem, there are numerous alternatives that compile to JS

In terms of performance, debugging, profiling, and simple functionality, compiling to JS is simply a work-around, not a solution.

> And yet, Google, Apple, AND Mozilla have all successfully introduced entirely new or significantly refactored VMs in the past few years.

Yes, because the old VMs were critically slow. Things like DOM manipulation aren't blocking problems the way they used to be.

> This is solvable; it HAS been solved.

Why? What critical problem requires a bytecode VM? Developers refusing to write in anything but their favorite language?

> In terms of performance, debugging, profiling, and simple functionality, compiling to JS is simply a work-around, not a solution.

This is solvable without alternative VMs. WebKit is working on CoffeeScript/other language debugging: http://www.infoq.com/news/2011/08/debug-languages-on-javascr...

> Why? What critical problem requires a bytecode VM? Developers refusing to write in anything but their favorite language?

Your argument was that it wasn't technically achievable because it would break the web, yet it's clear that it can be done and HAS been done.

I'll try to address this new argument.

JS isn't perfect, it will never be perfect, and the lack of a bytecode VM is a hindrance to experiments and production language implementations that can lead to better solutions for developers.

Look at the language design that has occurred elsewhere. I may not use Erlang, but I learned a lot from it. Clojure introduced a ton of interesting concurrency constructs (among other advances). C# demonstrated LINQ, and F# is OCaml revisited.

In all of these cases it has nothing to do with whiny developers "refusing to write in anything but their favorite language". We're simply attempting to advance the state of the art, because nothing is perfect, especially JavaScript.

> This is solvable without alternative VMs. WebKit is working on CoffeeScript/other language debugging:

It's a work-around, not a solution. JavaScript still isn't an efficient bytecode format, this won't solve performance issues. We've seen similar work on languages that compile down to C, and it's not an adequate solution to debugging, especially when the debuggers benefit from language-specific enhancements.

Excuse my ignorance, but what browser-based non-JS VM was introduced successfully? You mentioned this was done before, and I assume you mean it was done successfully, so just curious to know which one it is?

We were actually discussing JS VM replacement in the browser, related to:

> True, but the JS VMs we have today have been refined over 15+ years and switching to another risks breaking the web in profound ways.

The counter-point being that all the major browser vendors have swapped out their VM or performed significant rewrites in the past few years; it's clear that it's possible to implement a new VM and not "break the web in profound ways".

At the surface level, I could see how your position would appear logical.

However, the nature of the replacement VM doesn't really matter in the context of what we're describing here.

The problems of compatibility remain the same regardless of whether the target VM is a JS-specific VM, or a general purpose VM; reliance on undefined behavior, accidental changes in semantics, optimization bugs, and so on.

If browser makers were able to swap-out the VM, they've already demonstrated the ability to solve the exact same kind of compatibility problems they'd face here.

A VM that provides a standardized bytecode and execution model capable of executing most modern dynamic and static turing complete languages with sufficient performance. This requires more general facilities for common functionality required; refer to tail call support, JVM's invokedynamic, etc.

Or, shorthand, a general purpose browser VM.

Unless, of course, you're arguing that the above is not truly possible, in which case I'd argue that's exactly what Google is exploring via PNaCL, and has (if not completely efficiently) been implemented across existing VMs. The PNaCL choice of LLVM bitcode was likely in error, but regardless, "no such thing" is a stretch.

I'm not saying that it is impossible as clearly there have been good efforts being made. However there is no such thing implemented.

Which comes full circle to my original point, which is that other than Google, nobody with a vested interest is trying, and worse yet, they actively oppose progress on this front.