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Does anyone know of real (i.. no vaporware) implementations of ECMAScript targeting the .NET CLR/DLR? Ideally something like what Rhino is for Java. A solid port of Rhino running on .NET Framework / Mono Framework would be perfect.

I've only seen a handful of projects mentioned but never seen any come to light or in reality anything that I've ever been able to run script on. Here's what I know about already:

  • MSScriptControl ActiveX Control: AFAIK, this was Microsoft's last real ECMAScript-compliant implementaiton (runs JScript 5.7). I've integrated with MSScriptControl but don't consider COM interop to be an answer to this question. x64 is a killer for this option.

  • JScript.NET: I don't count JScript.NET as it could never successfully parse any of my real scripts. It seems to have trouble with closures.

  • Managed JScript: Sounds like what I want but it appears to be dead in the water. It was a major example implementation for the DLR but then got entangled with SilverLight and seems to have faded as a priority since 2007. Creditable sources on the status of this would be helpful.

  • MyJScript: Built as a tutorial implementation for the DLR. Anyone know how complete of an implementation this is?

  • Jint: JavaScript interpreter for .NET. Doesn't as of yet support Currying or try-catch-finally.

  • RemObjects Script for .NET: An interesting contender still in the works. I'm confused by their marketing as to what it will actually be, but it sounds like it might eventually be a fit. If anyone knows more about it that would be helpful as well.

  • V8 for .NET: This would be great if someone ported V8 to .NET. As far as I know there isn't a large effort around this either. The link is to an idea for calling into it from a managed C++ wrapper.

For background, I want to be able to execute JavaScript from within .NET; i.e. load up a set of scripts into context and call into that context and retrieve the execution results. Currently I jump through hoops to use MSScriptControl via cumbersome COM Interop. The inconsistency of COM makes it really tough for deployment and ensuring consistent execution.

I'd like to be able to execute reasonably complex JavaScript test harnesses from within .NET. This isn't for creating user macros or simple tiny scripts; I need a real JavaScript environment like Rhino. If the implementation was running on top of the CLR (rather than COM) this would really help with some of the current issues.

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Can you run rhino via ikvm? ikvm.net –  Stobor Jul 2 '09 at 7:16
JavaScript over Mozilla Rhino, over IKVM.NET over .NET. What a sandwich :) –  Ionuț G. Stan Jul 2 '09 at 9:35
Or Rhino over VMKit (llvm.org). –  Jared Updike Jul 3 '09 at 0:29
Jint does handle currying and exception now –  Sébastien Ros - MSFT Oct 26 '09 at 13:56
My bootlegged implementation is in the works... –  ChaosPandion Aug 25 '10 at 2:50
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9 Answers

up vote 15 down vote accepted

Currently, I've modified a version of the EcmaScript.NET inside my YUICompressor.NET port (project).

If you grab the source code from here, I've included my modified code in the project, which you can reference. This is the only source of code i've found in .NET which can handle parsing javascript, server side.

Unfortunately, I can't remember how I finally found it. It was a tough process, I must admit. I think i found some references Mozilla dev pages somewhere about Rhino (the java code) which led me to finding that C# .NET implimentation.

I had to modify it slighty to sync up with some changes the YUI Compressor guys did to their code branch. So the modified branch I have might not be the best .. but it's the closest I've seen to the original Java branch.

The original c# code for EcmaScript.NET hasn't been touched since 2007 ... at least for the downloads page.

Maybe this might help??


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Excellent, I appreciate the details. If it can handle scripts for YUI Compressor sounds like it should be sufficient for my stuff as well. If you're not wanting to maintain that as your primary objective, it might be easier to get others' help as its own project. I'd be more than happy to contribute any fixes / improvements I make. Thanks! –  mckamey Jul 3 '09 at 0:46
I certainly don't want to take ownership of the modified version so i'm happy to have it moved into codeplex, into a seperate project .. assuming the code base i have is .. er .. acceptable :) (I also prefer codeplex over google code :P ) –  Pure.Krome Jul 3 '09 at 1:03
It looks like EcmaScript.NET at Google Code ( code.google.com/p/ecmascript-net/ ) had some bug fixes ported in June 2008. It might be worth seeing if your changes would be accepted by the owner. –  mckamey Jul 6 '09 at 15:40
Is that a dead project, also? Also, I've released a new version of YUICompressor.NET yesterday :) –  Pure.Krome Jul 7 '09 at 0:20
Not dead but not being actively maintained. Owner says he's open to patches, might want help porting Rhino bug fixes. It would be great if he opens it wider and your fixes could make it into his repos so there was a singular source. Then your repos could focus on YUI Compressor, and others (I'd be willing) could contribute to the maintenance of ECMAScript.NET. –  mckamey Jul 7 '09 at 15:42
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Everyone seems to be beating their heads against this one:

Other Projects, Mostly Dead:

Crazy Method:

  • Rhino over IKVM (Mentioned in comments, but here's a link to more information about doing it.)
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+1 for IronJS. I will definitely be keeping an eye on it. It sounds like it is very early on though. Any indication of how well it works? –  mckamey Mar 5 '10 at 11:48
Domain is dead but the project is still going on ironjs.wordpress.com –  Diogo Gomes May 10 '11 at 15:44
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Nobody has mentioned jurassic http://jurassic.codeplex.com/ I do not know how good it is in general (performance, usability, etc) but at least it parses pretty complex scripts (other implementations do not) and it supports ECMAScript 5 spec. I just add the link here for reference.

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I added ActiveXObject support to Jurassic in the form of this project: jurascript.codeplex.com so you can reuse most old WSH/JScript scripts. Obviously, they should be thoroughly tested before assuming this will work without issue. :) –  aikeru Feb 15 '12 at 6:03
Jurassic is among the friendlier frameworks, and the performance is good too –  Surya Pratap Nov 7 '12 at 8:27
Does it work with Mono? –  Donny V. May 29 '13 at 0:06
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You should try Javascript .NET (http://javascriptdotnet.codeplex.com/) on Codeplex. They wrapped v8 with managed C++ and then you can use this library with a .NET application and it works like a charm. The open source offers some pretty good features if you ask me.


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Do you (or anyone else) know what sort of caveats there are with this implementation? Is it purely managed? Or does it require a particular processor architecture? I'm curious if it would run on Mono or some alternate CLR. –  mckamey Aug 25 '10 at 22:47
Sadly, you won't be able to run it on Mono since Managed C++ doesn't work on Linux so it won't work on Mono. Javascript .NET run on x86 platform since v8 is on x86 and sadly you won't be able to use Javascript .NET in a multi-thread application since v8 doesn't support well the feature. That's about all I know about the project. I used it for my personal application and works well so far. –  Deacon Frost Aug 26 '10 at 15:18
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Nobody's mentioned ClearScript, so ClearScript.

It's not an implementation; it's an interop wrapper that supports V8, JScript and VBScript, with a really nice API to call into them from .NET code.

Example code from the CodePlex page:

using System;
using Microsoft.ClearScript;
using Microsoft.ClearScript.V8;

// create a script engine
using (var engine = new V8ScriptEngine())
    // expose a host type
    engine.AddHostType("Console", typeof(Console));
    engine.Execute("Console.WriteLine('{0} is an interesting number.', Math.PI)");

    // expose a host object
    engine.AddHostObject("random", new Random());

    // expose entire assemblies
    engine.AddHostObject("lib", new HostTypeCollection("mscorlib", "System.Core"));

    // create a host object from script
        birthday = new lib.System.DateTime(2007, 5, 22);

    // use a generic class from script
        Dictionary = lib.System.Collections.Generic.Dictionary;
        dict = new Dictionary(lib.System.String, lib.System.Int32);
        dict.Add('foo', 123);

    // call a host method with an output parameter
    engine.AddHostObject("host", new HostFunctions());
        intVar = host.newVar(lib.System.Int32);
        found = dict.TryGetValue('foo', intVar.out);
        Console.WriteLine('{0} {1}', found, intVar);

    // create and populate a host array
        numbers = host.newArr(lib.System.Int32, 20);
        for (var i = 0; i < numbers.Length; i++) { numbers[i] = i; }
        Console.WriteLine(lib.System.String.Join(', ', numbers));

    // create a script delegate
        Filter = lib.System.Func(lib.System.Int32, lib.System.Boolean);
        oddFilter = new Filter(function(value) {
            return (value & 1) ? true : false;

    // use LINQ from script
        oddNumbers = numbers.Where(oddFilter);
        Console.WriteLine(lib.System.String.Join(', ', oddNumbers));

    // call a script function
    engine.Execute("function print(x) { Console.WriteLine(x); }");

    // examine a script object
    engine.Execute("person = { name: 'Fred', age: 5 }");
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You can take a look at Jint (http://jint.codeplex.com) which is an open-source ECMAScript interpreter.

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Haven't tried it out yet, but jint looks really promising! –  Chris Pietschmann Jul 13 '10 at 1:08
Does it work on Mono? –  Donny V. May 29 '13 at 0:10
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You can use Jscript.net and it will actually work with arbitrary javascript code; You just need to turn off "fast mode" by compiling with jsc /fast- bar.js

I have not tested this; I just noticed it while reading this post and figured it would be another reasonable solution. MSDN Has the docs for this option and what the limitations are if you don't use it.

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This one is probably the best one I've come across yet.

Plus its been built from the beginning with a Mono port in mind. It gives you full control over the power of the V8 engine from managed code.

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I prefer JINT rather than the others.

JINT may be slow, but it is easy to debug and to interact your own .NET classes. (It is hard to set [ComVisile] attributes every time for jscript.dll etc).

In terms of threading, JINT and Jurassic work as I expected. In order to work with JScript engine or Google V8, you have to pay attention to UI-threading issue.

However, JINT is out-dated in some aspect, because I have trouble to compile JQuery 1.5 or later.

I hope Jurassic can remove its limit to stick its own class to work with by creating 'AllowBob'sCLRClass=true'.

I have to re-write the entire class. It is hard...

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This thread is three years old, the information in it is probably out of date! –  durron597 Nov 15 '12 at 19:50
Yep. Ultimately, I just ended up using Rhino in Java in the long run. –  mckamey Nov 15 '12 at 20:44
Rhino 1.7R has nice performance also. I also play with it until Oracle to releases 'Nashorn' with new Java 8. –  Yone Nov 22 '12 at 5:44
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