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I can't find information on the web how W3C languages compile to machine code. I know that the gap between the web and the processor must be somehow the browser, but how does it work and what are the steps till Javascript is executed in the processor?
Links to scientific documents would be also greatly appreciated.
It's up to the implementation; the specification is the full description of the language and how it's supposed to work, implementations are free to satisfy that implementation in any way they like. Some implementations seem (from the outside) to run it purely as an interpreter in the old sense; others may or may not compile to bytecode; V8 (the JavaScript engine in Chrome, Chromium, Brave, Node.js, and others) used to compile to machine code (twice, for hotspots in the app), but now starts out parsing to bytecode and running it in an interpreter and only compiling hotspots as necessary (details). (There's also a V8 mode where it only interprets, which they're experimenting with for environments where compiling at runtime isn't an option, such as iOS where non-Apple apps aren't allowed to allocate executable memory.)
The V8 team (V8 being the JavaScript engine in Chromium and Chrome) periodically publish descriptions of how they get the fantastic speed out of V8 that they do. You may find some of that on the V8 blog.
Naturally, you can also kick around the code of any of the open-source implementations. V8 and SpiderMonkey (Mozilla's engine) are the two major open-source ones I know.
This may help : http://www.ecma-international.org/publications/standards/Ecma-262.htm
There is no spec for how to translate into bytecode (That is up to the browser developers) but there are specs about how the language should behave
For Firefox there's some specifications on its bytecodes:
https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey/Bytecodes
https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey/Internals/Bytecode
For V8 it's compiled to native code directly:
http://jayconrod.com/posts/51/a-tour-of-v8-full-compiler
Javascript (as it's name suggests) is a dynamic scripting language. Meaning that it's code is analysed and executed at runtime by the web-browser's Javascript engine.
It is up to the Web-browser, how it wants to deal with Javascript. Some may generate an intermediate language, or bytecode. Some may directly analyse and execute it.
Here are the steps to the simplest way to execute Javascript (parsing and executing at runtime):
Parsing and Preprocessing (recursive descent or otherwise)
Analysis
Execution
Chrome's Javascript Engine compiles Javascript to native platform-specific machine code (for optimum performance) It also has a Garbage Collection Mechanism.
In addition to the useful, specific answers already given, the phrase 'adaptive optimisation' is probably worth looking up if performance is your main interest. JavaScript and its interpreters are just the latest instance of systems that need to convert something else to machine code at runtime, so there's plenty of wider reading. The bytecode forms of Pascal, Smalltalk, Java, etc can easily enough be viewed as an intermediate form in the process of running a defined language on arbitrary hardware — Apple's SquirrelFish explicitly creates a bytecode and uses a JIT compiler on that, for example.
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Are there any Ruby / Python features that are blocking implementation of optimizations (e.g. inline caching) V8 engine has?
Python is co-developed by Google guys so it shouldn't be blocked by software patents.
Or this is rather matter of resources put into the V8 project by Google.
What blocks Ruby, Python to get Javascript V8 speed?
Nothing.
Well, okay: money. (And time, people, resources, but if you have money, you can buy those.)
V8 has a team of brilliant, highly-specialized, highly-experienced (and thus highly-paid) engineers working on it, that have decades of experience (I'm talking individually – collectively it's more like centuries) in creating high-performance execution engines for dynamic OO languages. They are basically the same people who also created the Sun HotSpot JVM (among many others).
Lars Bak, the lead developer, has been literally working on VMs for 25 years (and all of those VMs have lead up to V8), which is basically his entire (professional) life. Some of the people writing Ruby VMs aren't even 25 years old.
Are there any Ruby / Python features that are blocking implementation of optimizations (e.g. inline caching) V8 engine has?
Given that at least IronRuby, JRuby, MagLev, MacRuby and Rubinius have either monomorphic (IronRuby) or polymorphic inline caching, the answer is obviously no.
Modern Ruby implementations already do a great deal of optimizations. For example, for certain operations, Rubinius's Hash class is faster than YARV's. Now, this doesn't sound terribly exciting until you realize that Rubinius's Hash class is implemented in 100% pure Ruby, while YARV's is implemented in 100% hand-optimized C.
So, at least in some cases, Rubinius can generate better code than GCC!
Or this is rather matter of resources put into the V8 project by Google.
Yes. Not just Google. The lineage of V8's source code is 25 years old now. The people who are working on V8 also created the Self VM (to this day one of the fastest dynamic OO language execution engines ever created), the Animorphic Smalltalk VM (to this day one of the fastest Smalltalk execution engines ever created), the HotSpot JVM (the fastest JVM ever created, probably the fastest VM period) and OOVM (one of the most efficient Smalltalk VMs ever created).
In fact, Lars Bak, the lead developer of V8, worked on every single one of those, plus a few others.
There's a lot more impetus to highly optimize JavaScript interpretors which is why we see so many resources being put into them between Mozilla, Google, and Microsoft. JavaScript has to be downloaded, parsed, compiled, and run in real time while a (usually impatient) human being is waiting for it, it has to run WHILE a person is interacting with it, and it's doing this in an uncontrolled client-end environment that could be a computer, a phone, or a toaster. It HAS to be efficient in order to run under these conditions effectively.
Python and Ruby are run in an environment controlled by the developer/deployer. A beefy server or desktop system generally where the limiting factor will be things like memory or disk I/O and not execution time. Or where non-engine optimizations like caching can be utilized. For these languages it probably does make more sense to focus on language and library feature set over speed optimization.
The side benefit of this is that we have two great high performance open source JavaScript engines that can and are being re-purposed for all manner of applications such as Node.js.
A good part of it has to do with community. Python and Ruby for the most part have no corporate backing. No one gets paid to work on Python and Ruby full-time (and they especially don't get paid to work on CPython or MRI the whole time). V8, on the other hand, is backed by the most powerful IT company in the world.
Furthermore, V8 can be faster because the only thing that matters to the V8 people is the interpreter -- they have no standard library to work on, no concerns about language design. They just write the interpreter. That's it.
It has nothing to do with intellectual property law. Nor is Python co-developed by Google guys (its creator works there along with a few other committers, but they don't get paid to work on Python).
Another obstacle to Python speed is Python 3. Its adoption seems to be the main concern of the language developers -- to the point that they have frozen development of new language features until other implementations catch up.
On to the technical details, I don't know much about Ruby, but Python has a number of places where optimizations could be used (and Unladen Swallow, a Google project, started to implement these before biting the dust). Here are some of the optimizations that they planned. I could see Python gaining V8 speed in the future if a JIT a la PyPy gets implemented for CPython, but that does not seem likely for the coming years (the focus right now is Python 3 adoption, not a JIT).
Many also feel that Ruby and Python could benefit immensely from removing their respective global interpreter locks.
You also have to understand that Python and Ruby are both much heavier languages than JS -- they provide far more in the way of standard library, language features, and structure. The class system of object-orientation alone adds a great deal of weight (in a good way, I think). I almost think of Javascript as a language designed to be embedded, like Lua (and in many ways, they are similar). Ruby and Python have a much richer set of features, and that expressiveness is usually going to come at the cost of speed.
Performance doesn't seem to be a major focus of the core Python developers, who seem to feel that "fast enough" is good enough, and that features that help programmers be more productive are more important than features that help computers run code faster.
Indeed, however, there was a (now abandoned) Google project, unladen-swallow, to produce a faster Python interpreter compatible with the standard interpreter. PyPy is another project that intends to produce a faster Python. There is also Psyco, the forerunner of PyPy, which can provide performance boosts to many Python scripts without changing out the whole interpreter, and Cython, which lets you write high-performance C libraries for Python using something very much like Python syntax.
Misleading question. V8 is a JIT (a just in time compiler) implementation of JavaScript and in its most popular non-browser implementation Node.js it is constructed around an event loop. CPython is not a JIT & not evented. But these exist in Python most commonly in the PyPy project - a CPython 2.7 (and soon to be 3.0+) compatible JIT. And there are loads of evented server libraries like Tornado for example. Real world tests exist between PyPy running Tornado vs Node.js and the performance differences are slight.
I just ran across this question and there is also a big technical reason for the performance difference that wasn't mentioned. Python has a very large ecosystem of powerful software extensions, but most of these extensions are written in C or other low-level languages for performance and are heavily tied to the CPython API.
There are lots of well-known techniques (JIT, modern garbage collector, etc) that could be used to speed up the CPython implementation but all would require substantial changes to the API, breaking most of the extensions in the process. CPython would be faster, but a lot of what makes Python so attractive (the extensive software stack) would be lost. Case in point, there are several faster Python implementations out there but they have little traction compared to CPython.
Because of different design priorities and use case goals I believe.
In general main purpose of scripting (a.k.a. dynamic) languages is to be a "glue" between calls of native functions. And these native functions shall a) cover most critical/frequently used areas and b) be as effective as possible.
Here is an example:
jQuery sort causing iOS Safari to freeze
The freeze there is caused by excessive use of get-by-selector calls. If get-by-selector would be implemented in native code and effectively it will be no such problem at all.
Consider ray-tracer demo that is frequently used demo for V8 demonstration. In Python world it can be implemented in native code as Python provides all facilities for native extensions. But in V8 realm (client side sandbox) you have no other options rather than making VM to be [sub]effective as possible. And so the only option see ray-tracer implementation there is by using script code.
So different priorities and motivations.
In Sciter I've made a test by implementing pretty much full jQurey core natively. On practical tasks like ScIDE (IDE made of HTML/CSS/Script) I believe such solution works significantly better then any VM optimizations.
As other people have mentioned, Python has a performant JIT compiler in the form of PyPy.
Making meaningful benchmarks is always subtle, but I happen to have a simple benchmark of K-means written in different languages - you can find it here. One of the constraints was that the various languages should all implement the same algorithm and should strive to be simple and idiomatic (as opposed to optimized for speed). I have written all the implementations, so I know I have not cheated, although I cannot claim for all languages that what I have written is idiomatic (I only have a passing knowledge of some of those).
I do not claim any definitive conclusion, but PyPy was among the fastest implementations I got, far better than Node. CPython, instead, was at the slowest end of the ranking.
The statement is not exactly true
Just like V8 is just an implementation for JS, CPython is just one implementation for Python. Pypy has performances matching V8's.
Also, there the problem of perceived performance : since V8 is natively non blocking, Web dev leads to more performant projects because you save the IO wait. And V8 is mainly used for dev Web where IO is key, so they compare it to similar projects. But you can use Python in many, many other areas than web dev. And you can even use C extensions for a lot of tasks, such as scientific computations or encryption, and crunch data with blazing perfs.
But on the web, most popular Python and Ruby projects are blocking. Python, especially, has the legacy of the synchronous WSGI standard, and frameworks like the famous Django are based on it.
You can write asynchronous Python (like with Twisted, Tornado, gevent or asyncio) or Ruby. But it's not done often. The best tools are still blocking.
However, they are some reasons for why the default implementations in Ruby and Python are not as speedy as V8.
Experience
Like Jörg W Mittag pointed out, the guys working on V8 are VM geniuses. Python is dev by a bunch a passionate people, very good in a lot of domains, but are not as specialized in VM tuning.
Resources
The Python Software foundation has very little money : less than 40k in a year to invest in Python. This is kinda crazy when you think big players such as Google, Facebook or Apple are all using Python, but it's the ugly truth : most work is done for free. The language that powers Youtube and existed before Java has been handcrafted by volunteers.
They are smart and dedicated volunteers, but when they identify they need more juice in a field, they can't ask for 300k to hire a top notch specialist for this area of expertise. They have to look around for somebody who would do it for free.
While this works, it means you have to be very a careful about your priorities. Hence, now we need to look at :
Objectives
Even with the latest modern features, writing Javascript is terrible. You have scoping issues, very few collections, terrible string and array manipulation, almost no stdlist apart from date, maths and regexes, and no syntactic sugar even for very common operations.
But in V8, you've got speed.
This is because, speed was the main objective for Google, since it's a bottleneck for page rendering in Chrome.
In Python, usability is the main objective. Because it's almost never the bottleneck on the project. The scarce resource here is developer time. It's optimized for the developer.
Because JavaScript implementations need not care about backwards compatibility of their bindings.
Until recently the only users of the JavaScript implementations have been web browsers. Due to security requirements, only the web browser vendors had the privilege to extend the functionality by writing bindings to the runtimes. Thus there was no need keep the C API of the bindings backwards compatible, it was permissible to request the web browser developers update their source code as the JavaScript runtimes evolved; they were working together anyways. Even V8, which was a latecomer to the game, and also lead by a very very experienced developer, have changed the API as it became better.
OTOH Ruby is used (mainly) on the server-side. Many popular ruby extensions are written as C bindings (consider an RDBMS driver). In other words, Ruby would have never succeeded without maintaining the compatibility.
Today, the difference still exist to some extent. Developers using node.js are complaining that it is hard to keep their native extensions backwards compatible, as V8 changes the API over time (and that is one of the reasons node.js has been forked). IIRC ruby is still taking a much more conservative approach in this respect.
V8 is fast due to the JIT, Crankshaft, the type inferencer and data-optimized code. Tagged pointers, NaN-tagging of doubles.
And of course it does normal compiler optimizations in the middle.
The plain ruby, python and perl engines don't do neither of the those, just minor basic optimizations.
The only major vm which comes close is luajit, which doesn't even do type inference, constant folding, NaN-tagging nor integers, but uses similar small code and data structures, not as fat as the bad languages.
And my prototype dynamic languages, potion and p2 have similar features as luajit, and outperform v8. With an optional type system, "gradual typing", you could easily outperform v8, as you can bypass crankshaft. See dart.
The known optimized backends, like pypy or jruby still suffer from various over-engineering techniques.
I am confused about JavaScript engines right now. I know that V8 was a big deal because it compiled JavaScript to native code.
Then I started reading about Mozilla SpiderMonkey, which from what I understand is written in C and can compile JavaScript. So how is this different from V8 and if this is true, why does Firefox not do this?
Finally, does Rhino literally compile the JavaScript to Java byte code so you would get all the speed advantages of Java? If not, why do people not run V8 when writing scripts on their desktops?
There are various approaches to JavaScript execution, even when doing JIT. V8 and Nitro (formerly known as SquirrelFish Extreme) choose to do a whole-method JIT, meaning that they compile all JavaScript code down to native instructions when they encounter script, and then simply execute that as if it was compiled C code. SpiderMonkey uses a "tracing" JIT instead, which first compiles the script to bytecode and interprets it, but monitors the execution, looking for "hot spots" such as loops. When it detects one, it then compiles just that hot path to machine code and executes that in the future.
Both approaches have upsides and downsides. Whole-method JIT ensures that all JavaScript that is executed will be compiled and run as machine code and not interpreted, which in general should be faster. However, depending on the implementation it may mean that the engine spends time compiling code that will never be executed, or may only be executed once, and is not performance critical. In addition, this compiled code must be stored in memory, so this can lead to higher memory usage.
The tracing JIT as implemented in SpiderMonkey can produce extremely specialized code compared to a whole-method JIT, since it has already executed the code and can speculate on the types of variables (such as treating the index variable in a for loop as a native integer), where a whole-method JIT would have to treat the variable as an object because JavaScript is untyped and the type could change (SpiderMonkey will simply "fall off" trace if the assumption fails, and return to interpreting bytecode). However, SpiderMonkey's tracing JIT currently does not work efficiently on code with many branches, as the traces are optimized for single paths of execution. In addition, there's some overhead involved in monitoring execution before deciding to compile a trace, and then switching execution to that trace. Also, if the tracer makes an assumption that is later violated (such as a variable changing type), the cost of falling off trace and switching back to interpreting is likely to be higher than with a whole-method JIT.
V8 is the fastest, because it compiles all JS to machine code.
SpiderMonkey (what FF uses) is fast too, but compiles to an intermediate byte-code, not machine code. That's the major difference with V8. EDIT- Newer Firefox releases come with a newer variant of SpideMonkey; TraceMonkey. TraceMonkey does JIT compilation of critical parts, and maybe other smart optimizations.
Rhino compiles Javascript into Java classes, thus allowing you to basically write "Java" applications in Javascript. Rhino is also used as a way to interpret JS in the backend and manipulate it, and have complete code understanding, such as reflection. This is used for example by the YUI Compressor.
The reason why Rhino is used instead of V8 all over the place is probably because V8 is relatively new, so a lot of projects have already been using Rhino/Spidermonkey as their JS engine, for example Yahoo widgets. (I assume that's what you're referring to with "scripts on their desktops")
edit-
This link might also give some insight of why SpiderMonkey is so widely adopted.
Which Javascript engine would you embed in your application?
If you want to see how the various in-browser Javascript engines stack up, install Safari 4 (yes it runs on Windows now too!), Chrome V8, Firefox 3.5, and IE 8 (if you are on windows) and run the benchmark:
http://www2.webkit.org/perf/sunspider-0.9/sunspider.html
I believe as Pointy said above, the new Firefox 3.5 uses TraceMonkey that also compiles to intermedit code on the fly using some form of JIT. So it should compare to V8 somewhat favorably. At least it won't be 10x slower than V8 like Firefox 3 SpiderMonkey (without JIT) was.
For me... safari 4.0.3 was 2.5x faster than Tracemonky in Firefox 3.5.3 on Win XP. IE8 was much much slower. I don't have Chrome installed at the moment.
Don't know about Rhino compiling to java bytecode. If it's still interpreting the dynamic features of Javascript such as being able to add attributes to object instances at runtime (example obj.someNewAttribute="someValue" which is allowed in Javascript)... I'm not so sure that it's entirely "compiled" to bytecode, and you might not get any better performance other than you don't have to compile from Javascript source code text every time your Javascript runs. Remember that Javascript allows very dynamic syntax such as eval("x=10;y=20;z=x*y"); which means you can build up strings of code that get compiled at runtime. That's why I'd think Rhino would be mixed-mode interpreted/compiled even if you did compile to JVM bytecode.
The JVM is still an interpreter, albeit a very good one with JIT support. So I like to think of Rhino-on-JVM as 2 interpreter layers (interpreter-on-interpreter) or interpreter^2. Whereas most of your other Javascript engines are written in C, and as such should perform more like interpreter^1. Each interpreter layer can add 5-10x performance degradation as compared to C or C++ (ref Perl or Python or Ruby for example), but with JIT the performance hit can be much lower on the order of 2-4x. And the JVM has one of the most robust & mature JIT engines ever.
So your mileage will definitely vary and you probably would benefit from doing some serious benchmarks if you want a real answer for your intended application on your own hardware & OS.
Rhino can't be too awfully slow, since I know lots of folks are using it. I think it's main appeal is not its speed, but the fact that is easy-to-code/light-weight/embeddable/interpreter that has hooks into Java libraries, which makes it perfect for scripting/configuration/extensibility of your software project. Some text editors like UltraEdit are even embedding Javascript as an alternative macro scripting engine. Every programmer seems to be able to stumble through javascript pretty easily, so it's easy to pick up as well.
One advantage to Rhino is that it runs pretty much anywhere the JVM runs. In my experience, trying to get stand-alone TraceMonkey or SpiderMonkey to build & run from command line can be a bit painful on systems like Windows. And embedding in your own application can be even more time consuming. But the payback to having an embeddable language would be worth it for a big project, as compared to having to "roll your own" mini scripting solution if that's what you're looking to do.
Scripting with Rhino is really easy if you have Java and the rhino jar, you just write your javascript and run it from command line. I use it all the time for simple tasks.
To respond the question, why native code Vs Byte code...
The native code is faster and for google a strategic choice because they have plan to JS one of them at least is ChromeOS.
A good video about this question is posted on Channel9 with an interview with Lars Bak the man behind V8 can be found here
2022 Update
V8 as also SpiderMonkey do support MultiPass Compilation as also SinglePass Compilation.
Java Rhino got deprecated and replaced by a new concept called Truffle Framework it is part of the GraalVM Stack which is in fact a JVMCI added to the JVM where CI means Compiler Interface. That allows the Truffle Language Implementer Framework to Implement any Language and translate that to Java Byte Code in MultiPass and Single Pass. the ECMAScript implementation is called GraalJS and it comes in 2 Flavors
GraalJS the 1:1 Rhino Replacement including compatability mode for incremental adoption and graal-node a NodeJS Fork where v8 is replaced with the GraalJS Engine.
as sayed Truffle is a Polyglot Language Implementer Framework so that works with any GraalVM Supported Language.
hope that helps and makes some sense since the jar versions do most best work when the whole stack has aligned versions you should alaways install the complet stack:
https://github.com/graalvm/graalvm-ce-builds/releases
download and install that then use the so called gu command to add graaljs
follow the instructions here: https://github.com/oracle/graaljs
Yes GraalVM can in general Compile Single Binary Executeable Files of all Polyglot Languages this is called AOT Compilation it has faster boot times but less throughput it can also do JIT and it can do a mix of both.
At the moment, the only fully supported language, and the de-facto standard for DOM tree manipulation in the browser is JavaScript. It looks like it has deep design issues that make it a minefield of bugs and security holes for the novice.
Do you know of any existent or planned initiative to introduce a better (redesigned) language of any kind (not only javascript) for DOM tree manipulation and HTTP requests in next generation browsers? If yes, what is the roadmap for its integration into, say, Firefox, and if no, for what reasons (apart of interoperability) should be JavaScript the only supported language on the browser platform?
I already used jQuery and I also read "javascript: the good parts". Indeed the suggestions are good, but what I am not able to understand is: why only javascript? On the server-side (your-favourite-os platform), we can manipulate a DOM tree with every language, even fortran. Why does the client side (the browser platform) support only javascript?
The problem with javascript is not the language itself - it's a perfectly good prototyped and dynamic language. If you come from an OO background there's a bit of a learning curve, but it's not the language's fault.
Most people assume that Javascript is like Java because it has similar syntax and a similar name, but actually it's a lot more like lisp. It's actually pretty well suited to DOM manipulation.
The real problem is that it's compiled by the browser, and that means it works in a very different way depending on the client.
Not only is the actual DOM different depending on the browser, but there's a massive difference in performance and layout.
Edit following clarification in question
Suppose multiple interpreted languages were supported - you still have the same problems. The various browsers would still be buggy and have different DOMs.
In addition you would have to have an interpreter built into the browser or somehow installed as a plug in (that you could check for before you served up the page) for each language. It took ages to get Javascript consistent.
You can't use compiled languages in the same way - then you're introducing an executable that can't easily be scrutinised for what it does. Lots of users would choose not to let it run.
OK, so what about some sort of sandbox for the compiled code? Sounds like Java Applets to me. Or ActionScript in Flash. Or C# in Silverlight.
What about some kind of IL standard? That has more potential. Develop in whatever language you want and then compile it to IL, which the browser then JITs.
Except, Javascript is kind of already that IL - just look at GWT. It lets you write programs in Java, but distribute them as HTML and JS.
Edit following further clarification in question
Javascript isn't, or rather wasn't, the only language supported by browsers: back in the Internet Explorer dark ages you could choose between Javascript or VBScript to run in IE. Technically IE didn't even run Javascript - it ran JScript (mainly to avoid having to pay Sun for the word java, Oracle still own the name Javascript).
The problem was that VBScript was proprietary to Microsoft, but also that it just wasn't very good. While Javascript was adding functionality and getting top rate debugging tools in other browsers (like FireBug) VBScript remained IE-only and pretty much un-debuggable (dev tools in IE4/5/6 were none existent). Meanwhile VBScript also expanded to become a pretty powerful scripting tool in the OS, but none of those features were available in the browser (and when they were they became massive security holes).
There are still some corporate internal applications out there that use VBScript (and some rely on those security holes), and they're still running IE7 (they only stopped IE6 because MS finally killed it off).
Getting Javascript to it's current state has been a nightmare and has taken 20 years. It still doesn't have consistent support, with language features (specified in 1999) still missing from some browsers and lots of shims being required.
Adding an alternate language for interpreting in browsers faces two major problems:
Getting all the browser vendors to implement the new language standard - something they still haven't managed for Javascript in 20 years.
A second language potentially dilutes the support you already have, allowing (for instance) IE to have second rate Javascript support but great VBScript (again). I really don't want to be writing code in different languages for different browsers.
It should be noted that Javascript isn't 'finished' - it's still evolving to become better in new browsers. The latest version is years ahead of of the browsers' implementations and they're working on the next one.
Compile to Javascript
For now, using a language which compiles to Javascript seems to be the only realistic way to reach all the platforms while writing smarter code, and this will likely remain the case for a long time. With any new offering, there will always be some reason why one or more vendors will not rush to ship it.
(But I don't really think this is a problem. Javascript has been nicely optimized by now. Machine code is also unsafe if written by hand, but works fine as a compile target and execution language.)
So many options
There is an ever growing pool of languages that compile to Javascript. A fairly comprehensive list can be found here:
List of languages that compile to JS on the Coffeescript Wiki
Noteworthy
I will mention a few I think are noteworthy (while no doubt neglecting some gems which I am unaware of):
Spider appeared in 2016. It claims to take the best ideas of Go, Swift, Python, C# and CoffeeScript. It isn't typesafe, but it does have some minor safety features.
Elm: Haskell may be the smartest language of them all, and Elm is a variant of Haskell for Javascript. It is highly type-aware and concise, and offers Functional Reactive Programming as a neat alternative to reactive templates or MVC spaghetti. But it may be quite a shock for procedural programmers.
Google's Go is aimed at conciseness, simplicity, and safety. Go code can be compiled into Javascript by GopherJS.
Dart was Google's later attempt to replace Javascript. It offers interfaces and abstract classes through a C/Java-like syntax with optional typing.
Haxe is like Flash's ActionScript, but it can target multiple languages so your code can be re-used in Java, C, Flash, PHP and Javascript programs. It offers type-safe and dynamic objects.
Opalang adds syntactic sugar to Javascript to provide direct database access, smart continuations, type-checking and assist with client/server separation. (Tied to NodeJS and MongoDB.)
GorillaScript, "a compile-to-JavaScript language designed to empower the user while attempting to prevent some common errors." is akin to Coffeescript but more comprehensive, providing a bunch of extra features to increase safety and reduce repetitive boilerplate patterns.
LiteScript falls somewhere inbetween Coffeescript and GorillaScript. It offers async/yield syntax for "inline" callbacks, and checking for variable typos.
Microsoft's TypeScript is a small superset of Javascript that lets you place type-restrictions on function arguments, which might catch a few bugs. Similarly BetterJS allows you to apply restrictions, but in pure Javascript, either by adding extra calls or by specifying types in JSDoc comments. And now Facebook has offered Flow which additionally performs type inference.
LiveScript is a spin-off from Coffeescript that was popular for its brevity but does not look very readable to me. Probably not the best for teams.
How to choose?
When choosing an alternative language, there are some factors to consider:
If other developers join your project in future, how long will it take them to get up to speed and learn this language, or what are the chances they know it already?
Does the language have too few features (code will still be full of boilerplate) or too many features (it will take a long time to master, and until then some valid code may be undecipherable)?
Does it have the features you need for your project? (Does your project need type-checking and interfaces? Does it need smart continuations to avoid nested callback hell? Is there a lot of reactivity? Might it need to target other environments in future?)
The future...
Jeff Walker has written a thought-provoking series of blog posts about "the Javascript problem", including why he thinks neither TypeScript, nor Dart nor Coffeescript offer adequate solutions. He suggests some desirable features for an improved language in the conclusion.
should be JavaScript the only supported language on the browser platform ?
Yes and no. There is an alternative out there called Dart by Google which does compile to JavaScript and just like jQuery it tries to make DOM manipulation a bit easier. It may be fun to experiment, check it out.
From Google see The dart language
From Microsoft see TypeScript language
See also
Elm
Kal
It is true that Javascript was at one point notoriously hard to deal with but the web development community has come a long way since. Instead, I would encourage you to have a look at jQuery. It's easy and abstracts away all the various problems.
And there really are no alternatives that work across the board. Flash comes to mind but that too is ECMA script and it's probably over kill for most things.
Short term, I'd use things like jQuery to hide the browser incompatibilities. Long term, technologies like Silverlight or Adobe AIR may make this a very different minefield (but still a minefield) in the future.
Doug Crockford gave a talk to Google detailing the bad and good parts of JavaScript and its future. It actually hasn't changed much at all since 1999--which can be said to be a good thing (pretty much all browsers can run the same code as long as you're aware of their limitations) and Doug shows where the good parts were mostly misunderstandings that turn out to be very powerful.
For DOM manipuluation, look at JQuery as a client-side library that replaces most of the awful DOM API with operations that are a pain to write to pretty elegant bits of code that are easier to write.
If you're thinking that JavaScript has deep issues, I recommend Doug Crockford's book, JavaScript: The Good Parts. (Or Google for "Crockford JavaScript" to find several video presentations he's done.) Crockford sketches out a safe subset and set of practices, and specifically lists some parts of the language to avoid.
I'm unaware of plans to replace JavaScript as the de facto means of manipulating the DOM. So best learn to use it safely and well.
In terms of client side Javascript is the only way to manipulate the DOM. In terms of server side there are a multitude of ways.
Internet Explorer supports pluggable scripting languages, although the only one reliably included with IE besides JScript is VBScript.
As far as I have seen, there seems to be a general sort of bias toward dynamic languages in the browser, and JavaScript seems to fill this need adequately enough that network effects make any other language a non-starter. The language is actually quite powerful, though its implementation in browsers leaves much to be desired.
If you're willing to restrict your customers/visitors to specific browsers, and possibly willing to require them to install a plug-in, you could look at MS Silverlight -- a readable overview is on wikipedia. With Silverlight 2, you can run, client-side, code you've written in C#, IronPython, IronRuby, VB.NET, etc; the free Moonlight clone of Silverlight, from the Mono project, promises to bring the same functionality to Linux.
In practice, most developers of web apps and sites prefer to reach wider audiences than Silverlight (and eventually Moonlight) can currently deliver -- which means sticking with Javascript, or possibly Flash (which uses a similar programming language, Actionscript).
So, gaining substantial mindshare, adoption and traction for anything else is proving to be an uphill fight even for Microsoft with its large groups of engineers and marketing budgets and a free-software project on the side (to possibly ease worries about proprietary lock-in) -- which may help explain why there's very little interest, e.g. on the part of the Mozilla Foundation, in pushing towards such a goal. "Apart from interoperability", you say: but clearly the issue of interoperability is THE biggie here, given what we observe wrt Silverlight's progress...
As already said, you have Flash (ActionScript, which is a derived language from Javascript) and Silverlight/Moonlight (IronPython, IronRuby, JScript, VBScript, C#) that can run in the browser via plugins (the first one being much more ubiquitous).
There is also another alternative if you like Ruby: HotRuby, it's a ruby implementation in javascript that will run in the browser. It is not very mature yet, but you can have a look at it.
One thing I haven't seen mentioned (oh, I see Alcides mentioned HotRuby while I was writing and Nosredna mentioned GWT and Script#) and would like to throw out there is there are a number of implementations of [insert language]-on-JavaScript (eg. translators that allow you to convert Ruby, Python, C#, Java, Obj-J/Cappuccino [similar to Obj-C/Cocoa] or Processing [for Canvas] to JavaScript either on the client or before deployment [and some of which also feature various abstraction libraries]). Of course there's a performance overhead if it is being translated on the client, but if you are more comfortable with another language it will allow you some flexibility.
Personally, though, I recommend learning to love JavaScript. It's an excellent, powerful language, and pretty elegant once you get to know it. I'm facing the opposite dilemma, chomping at the bit to have a capable server-side JavaScript/DOM solution that meets all of my needs. /unsolicited opinion
JavaScript is the English language of the web. English historically spread because it had a strong navy conquering various countries. This is comparable to big companies that conquered the web with JavaScript. It's a language clobbered together from multiple European sources (Greek, Latin, Germanic languages, French even some Chinese and Indian words). JavaScript borrowed a lot of concepts throughout the years from other languages (structural, OO, functional). English is spoken in different places with slight variations in dialect and accent, that can render understanding difficult. Just like JavaScript has different browsers interpreting it a bit differently.
Even though English is easy to learn initially, it has very inconsistent pronunciation and more exceptions than rules. Just like JavaScript it's always there to offer a surprise.
Despite the different accents, JavaScript is the lingua franca of the web. Just like you might not be English and write here in English, every web browser has a certain degree of English understanding. IE6 is like the guy who says on his resume that he's fluent, but only went to a two week course on English as a foreign language.
There have been attempts to supplant English as the worlds main language, e.g. Esperanto. But all of them failed, because most people on earth speak some English. In the same way it will be difficult to introduce better alternatives to JavaScript.
Jquery (still javascript but) it will really help you they have support for almost all the browsers and it isn't really that hard to learn :)
No. JavaScript is it, but it will evolve. The next version is "JavaScript Harmony," and you can learn more if you Google that.
Now and then someone suggests putting a byte code interpreter into the browsers alongside JavaScript. Probably won't happen, at least for awhile.
I happen to love JavaScript. But there are other solutions, including GWT, which compiles Java to JavaScript and Script#, which compiles C# to JavaScript.
I don't think Javascript will be replaced any time soon. For a completely different approach to rich clients, you might want to investigate Flex, which is a Flash-based technology.
Maybe something like haxe (see haxe.org) could help you. It is a language which seems cleaner than JavaScript and can be compiled down to JavaScript, so it can be run inside a browser.
I know that this is not a direct answer to your question, but I thought it might be interesting for you, nevertheless.
Many people understand that Javascript isn't best and prettiest language ever. However, it is currently supported by browsers, and thus it will be extremely hard to introduce a different language. We simply don't need another browser war.
This explains why I know of no plans of switching to a different client-side language.
But I think Javascript isn't so bad if you start thinking about DOM model and how would one work with it. Many things that are messy with JS are the result of the way DOM model works.
Would it not make sense to support a set of languages (Java, Python, Ruby, etc.) by way of a standardized virtual machine hosted in the browser rather than requiring the use of a specialized language -- really, a specialized paradigm -- for client scripting only?
To clarify the suggestion, a web page would contain byte code instead of any higher-level language like JavaScript.
I understand the pragmatic reality that JavaScript is simply what we have to work with now due to evolutionary reasons, but I'm thinking more about the long term. With regard to backward compatibility, there's no reason that inline JavaScript could not be simultaneously supported for a period of time and of course JavaScript could be one of the languages supported by the browser virtual machine.
Well, yes. Certainly if we had a time machine, going back and ensuring a lot of the Javascript features were designed differently would be a major pastime (that, and ensuring the people who designed IE's CSS engine never went into IT). But it's not going to happen, and we're stuck with it now.
I suspect, in time, it will become the "Machine language" for the web, with other better designed languages and APIs compile down to it (and cater for different runtime engine foibles).
I don't think, however, any of these "better designed languages" will be Java, Python or Ruby. Javascript is, despite the ability to be used elsewhere, a Web application scripting language. Given that use case, we can do better than any of those languages.
I think JavaScript is a good language, but I would love to have a choice when developing client-side web applications. For legacy reasons we're stuck with JavaScript, but there are projects and ideas looking for changing that scenario:
Google Native Client: technology for running native code in the browser.
Emscripten: LLVM bytecode compiler to javascript. Allows LLVM languages to run in the browser.
Idea: .NET CLI in the browser, by the creator of Mono: http://tirania.org/blog/archive/2010/May-03.html
I think we will have JavaScript for a long time, but that will change sooner or later. There are so many developers willing to use other languages in the browser.
Answering the question - No, it would not make sense.
Currently the closest things we have to a multi-language VM are the JVM and the CLR. These aren't exactly lightweight beasts, and it would not make sense to try and embed something of this size and complexity in a browser.
Let's examine the idea that you could write a new, multilanguage VM that would be better than the existing solution.
You're behind on stability.
You're behind on complexity (way, way, behind because you're trying to generalize over multiple languages)
You're behind on adoption
So, no, it doesn't make sense.
Remember, in order to support these languages you're going to have to strip down their APIs something fierce, chopping out any parts that don't make sense in the context of a browser script. There are a huge number of design decisions to be made here, and a huge opportunity for error.
In terms of functionality, we're probably only really working with the DOM anyway, so this is really an issue of syntax and language idom, at which point it does make sense to ask, "Is this really worth it?"
Bearing in mind, the only thing we're talking about is client side scripting, because server side scripting is already available in whatever language you like. It's a relatively small programming arena and so the benefit of bringing multiple languages in is questionable.
What languages would it make sense to bring in? (Warning, subjective material follows)
Bringing in a language like C doesn't make sense because it's made for working with metal, and in a browser there isn't much metal really available.
Bringing in a language like Java doesn't make sense because the best thing about it is the APIs anyway.
Bringing in a language like Ruby or Lisp doesn't make sense because JavaScript is a powerful dynamic language very close to Scheme.
Finally, what browser maker really wants to support DOM integration for multiple languages? Each implementation will have its own specific bugs. We've already walked through fire dealing with differences between MS Javascript and Mozilla Javascript and now we want to multiply that pain five or six-fold?
It doesn't make sense.
On Windows, you can register other languages with the Scripting Host and have them available to IE. For example VBScript is supported out of the box (though it has never gained much popularity as it is for most purposes even worse than JavaScript).
The Python win32 extensions allowed one to add Python to IE like this quite easily, but it wasn't really a good idea as Python is quite difficult to sandbox: many language features expose enough implementation hooks to allow a supposedly-restricted application to break out.
It is a problem in general that the more complexity you add to a net-facing application like the browser, the greater likelihood of security problems. A bunch of new languages would certainly fit that description, and these are new languages that are also still developing fast.
JavaScript is an ugly language, but through careful use of a selective subset of features, and support from suitable object libraries, it can generally be made fairly tolerable. It seems incremental, practical additions to JavaScript are the only way web scripting is likely to move on.
I would definitely welcome a standard language independent VM in browsers (I would prefer to code in a statically typed language).
(Technically) It's quite doable gradually: first one major browser supports it and server has the possibility to either send bytecode if current request is from compatible browser or translate the code to JavaScript and send plain-text JavaScript.
There already exist some experimental languages that compile to JavaScript, but having a defined VM would (maybe) allow for better performance.
I admit that the "standard" part would be quite tricky, though. Also there would be conflicts between language features (eg. static vs. dynamic typing) concerning the library (assuming the new thing would use same library). Therefore I don't think it's gonna happen (soon).
If you feel like you are getting your hands dirty, then you have either been brainwashed, or are still feeling the after affects of the "DHTML years". JavaScript is very powerful, and is suited well for its purpose, which is to script interactivity client side. This is why JavaScript 2.0 got such a bad rap. I mean, why packages, interfaces, classes, and the like, when those are clearly aspects of server-side languages. JavaScript is just fine as a prototype-based language, without being full-blown object oriented.
If there is a lack of seamlessness to your applications because the server-side and client-side are not communicating well, then you might want to reconsider how you architect your applications. I have worked with extremely robust Web sites and Web applications, and I have never once said, "Hmm, I really wish JavaScript could do (xyz)." If it could do that, then it wouldn't be JavaScript -- it would be ActionScript or AIR or Silverlight. I don't need that, and neither do most developers. Those are nice technologies, but they try to solve a problem with a technology, not a... well, a solution.
I don't think that a standard web VM is that inconceivable. There are a number of ways you could introduce a new web VM standard gracefully and with full legacy support, as long as you ensure that any VM bytecode format you use can be quickly decompiled into javascript, and that the resulting output will be reasonably efficient (I would even go so far as to guess that a smart decompiler would probably generate better javascript than any javascript a human could produce themselves).
With this property, any web VM format could be easily decompiled either on the server (fast), on the client (slow, but possible in cases where you have limited control of the server), or could be pre-generated and loaded dynamically by either the client or the server (fastest) for browsers that don’t natively support the new standard.
Those browsers that DO natively support the new standard would benefit from increased speed of the runtime for web vm based apps. On top of that, if browsers base their legacy javascript engines on the web vm standard (i.e. parsing javascript into the web vm standard and then running it), then they don’t have to manage two runtimes, but that’s up to the browser vendor.
While Javascript is the only well-supported scripting language you can control the page directly from, Flash has some very nice features for bigger programs. Lately it has a JIT and can also generate bytecode on the fly (check out runtime expression evaluation for an example where they use flash to compile user-input math expressions all the way to native binary). The Haxe language gives you static typing with inference and with the bytecode generation abilities you could implement almost any runtime system of your choice.
Quick update on this old question.
Everyone who affirmed that a "web page would contain byte code instead of any higher-level language like JavaScript" "won't happen".
June 2015 the W3C announced WebAssembly that is
a new portable, size- and load-time-efficient format suitable for
compilation to the web.
This is still experimental, but there is already some prototypal implementation in Firefox nightly and Chrome Canary and there is already some demonstration working.
Currently, WebAssembly is mostly designed to be produced from C/C++, however
as WebAssembly evolves it will support more languages than C/C++, and we hope that other compilers will support it as well.
I let you have a closer look at the official page of the project, it is truly exciting!
this question resurfaces regularly. my stance on this is:
A) wont happen and B) is already here.
pardon, what? let me explain:
ad A
a VM is not just some sort of universal magical device. most VMs are optimized for a certain language and certain language features. take the JRE/Java (or LLVM): optimized for static typing, and there are definitely problems and downsides when implementing dynamic typing or other things java didn't support in the first place.
so, the "general multipurpose VM" that supports lots of language features (tail call optimization, static & dynamic typing, foo bar boo, ...) would be colossal, hard to implement and probably harder to optimize to get good performance out of it. but i'm no language designer or vm guru, maybe i'm wrong: it's actually pretty easy, only nobody had the idea yet? hrm, hrm.
ad B
already here: there may not be a bytecode compiler/vm, but you don't actually need one. afaik javascript is turing complete, so it should be possible to either:
create a translator from language X to javascript (e.g. coffeescript)
create a interpreter in javascript that interprets language X (e.g. brainfuck). yes, performance would be abysmal, but hey, can't have everything.
ad C
what? there wasn't a point C in the first place!? because there isn't ... yet. google NACL. if anyone can do it, it's google. as soon google gets it working, your problems are solved. only, uh, it may never work, i don't know. the last time i read about it there were some unsolved security problems of the really tricky kind.
apart from that:
javascript's been there since ~1995 = 15 years. still, browser implementations differ today (although at least it's not insufferable anymore). so, if you start something new yet, you might have a version working cross browser around 2035. at least a working subset. that only differs subtly. and needs compatibility libs and layers. no point in not trying to improve things though.
also, what about readable source code? i know a lot of companies would prefer not to serve their code as "kind-of" open source. personally, i'm pretty happy i'm able to read the source if i suspect something fishy or want to learn from it. hooray for source code!
Indeed. Silverlight is effectively just that - a client side .Net based VM.
There are some errors in your reasoning.
A standard virtual machine in a standard browser will never be standard. We have 4 browsers, and IE has conflicting interests with regard to 'standard'. The three others are evolving fast but adoption rate of new technologies is slow. What about browsers on phones, small devices, ...
The integration of JS in the different browsers and its past history leads you to under-estimating the power of JS. You pledge a standard, but disapprove JS because standard didn't work out in the early years.
As told by others, JS is not the same as AIR/.NET/... and the like. JS in its current incarnation perfectly fits its goals.
In the long term, Perl and Ruby could well replace javascript. Yet the adoption of those languages is slow and it is known that they will never take over JS.
How do you define best? Best for the browser, or best for the developer? (Plus ECMAScript is different than Javascript, but that is a technicality.)
I find that JavaScript can be powerful and elegant at the same time. Unfortunately most developers I have met treat it like a necessary evil instead of a real programming language.
Some of the features I enjoy are:
treating functions as first class citizens
being able to add and remove functions to any object at any time (not useful much but mind blowing when it is)
it is a dynamic language.
It's fun to deal with and it is established. Enjoy it while it is around because while it may not be the "best" for client scripting it is certainly pleasant.
I do agree it is frustrating when making dynamic pages because of browser incompatibilities, but that can be mitigated by UI libraries. That should not be held against JavaScript itself anymore than Swing should be held against Java.
JavaScript is the browser's standard virtual machine. For instance, OCaml and Haskell now both have compilers that can output JavaScript. The limitation is not JavaScript the language, the limitation is the browser objects accessible via JavaScript, and the access control model used to ensure you can safely run JavaScript without compromising your machine. The current access controls are so poor, that JavaScript is only allowed very limited access to browser objects for safety reasons. The Harmony project is looking to fix that.
It's a cool idea. Why not take it a step further?
Write the HTML parser and layout engine (all the complicated bits in the browser, really) in the same VM language
Publish the engine to the web
Serve the page with a declaration of which layout engine to use, and its URL
Then we can add features to browsers without having to push new browsers out to every client - the relevant new bits would be loaded dynamically from the web. We could also publish new versions of HTML without all the ridiculous complexity of maintaining backwards compatibility with everything that's ever worked in a browser - compatibility is the responsibility of the page author. We also get to experiment with markup languages other than HTML. And, of course, we can write fancy JIT compilers into the engines, so that you can script your webpages in any language you want.
I would welcome any language besides javascript as possible scripting language.
What would be cool is to use other languages then Javascript. Java would probably not be a great fit between the tag but languages like Haskell, Clojure, Scala, Ruby, Groovy would be beneficial.
I came a cross Rubyscript somewhile ago ...
http://almaer.com/blog/running-ruby-in-the-browser-via-script-typetextruby and http://code.google.com/p/ruby-in-browser/
Still experimental and in progress, but looks promising.
For .Net I just found: http://www.silverlight.net/learn/dynamic-languages/ Just found the site out, but looks interesting too. Works even from my Apple Mac.
Don't know how good the above work in providing an alternative for Javascript, but it looks pretty cool at first glance. Potentially, this would allow one to use any Java or .Net framework natively from the browser - within the browser's sandbox.
As for safety, if the language runs inside the JVM (or .Net engine for that matter), the VM will take care of security so we don't have to worry about that - at least not more then we should for anything that runs inside the browser.
Probably, but to do so we'd need to get the major browsers to support them. IE support would be the hardest to get. JavaScript is used because it is the only thing you can count on being available.
The vast majority of the devs I've spoken to about ECMAScript et. al. end up admitting that the problem isn't the scripting language, it's the ridiculous HTML DOM that it exposes. Conflating the DOM and the scripting language is a common source of pain and frustration regarding ECMAScript. Also, don't forget, IIS can use JScript for server-side scripting, and things like Rhino allow you to build free-standing apps in ECMAScript. Try working in one of these environments with ECMAScript for a while, and see if your opinion changes.
This kind of despair has been going around for some time. I'd suggest you edit this to include, or repost with, specific issues. You may be pleasantly surprised by some of the relief you get.
A old site, but still a great place to start: Douglas Crockford's site.
Well, we have already VBScript, don't we? Wait, only IE supports it!
Same for your nice idea of VM. What if I script my page using Lua, and your browser doesn't have the parser to convert it to bytecode? Of course, we could imagine a script tag accepting a file of bytecode, that even would be quite efficient.
But experience shows it is hard to bring something new to the Web: it would take years to adopt a radical new change like this. How many browsers support SVG or CSS3?
Beside, I don't see what you find "dirty" in JS. It can be ugly if coded by amateurs, propagating bad practice copied elsewhere, but masters shown it can be an elegant language too. A bit like Perl: often looks like an obfuscated language, but can be made perfectly readable.
Check this out http://www.visitmix.com/Labs/Gestalt/ - lets you use python or ruby, as long as the user has silverlight installed.
This is a very good question.
It's not the problem only in JS, as it is in the lack of good free IDEs for developing larger programs in JS. I know only one that is free: Eclipse. The other good one is Microsoft's Visual Studio, but not free.
Why would it be free? If web browser vendors want to replace desktop apps with online apps (and they want) then they have to give us, the programmers, good dev tools. You can't make 50,000 lines of JavaScript using a simple text editor, JSLint and built-in Google Chrome debugger. Unless you're a macohist.
When Borland made an IDE for Turbo Pascal 4.0 in 1987, it was a revolution in programming. 24 years have passed since. Shamefully, in the year 2011 many programmers still don't use code completion, syntax checking and proper debuggers. Probably because there are so few good IDEs.
It's in the interest of web browser vendors to make proper (FREE) tools for programmers if they want us to build applications with which they can fight Windows, Linux, MacOS, iOS, Symbian, etc.
Realistically, Javascript is the only language that any browsers will use for a long time, so while it would be very nice to use other languages, I can't see it happening.
This "standardised VM" you talk of would be very large and would need to be adopted by all major browsers, and most sites would just continue using Javascript anyway since it's more suited to websites than many other browsers.
You would have to sandbox each programming language in this VM and reduce the amount of access each language has to the system, requiring a lot of changes in the languages and removal or reimplementation of many features. Whereas Javascript already has this in mind, and has done a for a long time.
Maybe you're looking for Google's Native Client.
In a sense, having a more expressive language like Javascript in the browser instead of something more general like Java bytecode has meant a more open web.
I think this is not so easy issue. We can say that we're stuck with JS, but is it really so bad with jQuery, Prototype, scriptaculous, MooTools, and all fantastic libraries?
Remember, JS is lightweight, even more so with V8, TraceMonkey, SquirrelFish - new Javascript engines used in modern browsers.
It is also proved - yeah, we know it has problems, but we have lots of these sorted out, like early security problems. Imaging allowing your browser to run Ruby code, or anything else. Security sandbox would have to be done for scratch. And you know what? Python folks already failed two times at it.
I think Javascript is going to be revised and improved over time, just like HTML and CSS is. The process may be long, but not everything is possible in this world.
I don't think you "understand the pragmatic issue that JavaScript is simply what we have to work with now". Actually it is very powerful language. You had your Java applet in browser for years, and where is it now?
Anyhow, you don't need to "get dirty" to work on client. For example, try GWT.
... you mean...
Java and Java applet
Flash and Adobe AIR
etc..
In general, any RIA framework can fill your needs; but for every one there's a price to pay for using it ( ej. runtime avalible on browser or/and propietary or/and less options than pure desktop )
http://en.wikipedia.org/wiki/List_of_rich_internet_application_frameworks
For developing Web with any non-web languaje, you've GWT: develop Java, compile to Javascript
Because they all have VMs with bytecode interpreters already, and the bytecode is all different too. {Chakra(IE), Firefox (SpiderMonkey), Safari (SquirrelFish), Opera(Carakan).
Sorry , I think Chrome (V8) compiles down to IA32 machine code.
well, considering all browsers already use a VM, I don't think it will be that difficult to make a VM language for the web.
I think it would greatly help for a few reasons:
1. since the server compiles the code, the amount of data sent is smaller and the client doesn't waist time on compiling the code.
2. since the server can compile the code in preparation and store it, unlike the client which tries to waist as little time quickly compiling the JS, it can make better code optimizations.
3. compiling a language to byte code is way easier then transpiling to JS.
as a final note (as someone already said in another comment), HTML and CSS compile down to a simpler language, not sure if it counts as byte code, but you could also send compiled html and css from the server to the client which would reduce parse and fetch times
IMO, JavaScript, the language, is not the problem. JavaScript is actually quite an expressive and powerful language. I think it gets a bad rep because it's not got classical OO features, but for me the more I go with the prototypal groove, the more I like it.
The problem as I see it is the flaky and inconsistent implementations across the many browsers we are forced to support on the web. JavaScript libraries like jQuery go a long way towards mitigating that dirty feeling.