Can JScript.NET be used to script a .NET application?

Question

Since MS appears to have killed Managed JavaScript in the latest DLR for both server-side (ASP.NET Futures) and client-side (Silverlight), has anyone successfully used non-obsolete APIs to allow scripting of their application objects with JScript.NET and/or can explain how to do so? A Mono/JScript solution might also be acceptable, if it is stable and meets the requriements below.

We are interested in upgrading off of a script host which uses the Microsoft JScript engine and ActiveScript APIs to something with more performance and easier extensibility. We have over 16,000 server-side scripts weighing in at over 42MB of source, so rewriting into another scripting language is out of the question.

Our specific requirements are:

• Noteably better performance than the Microsoft JScript (ActiveScript) engine
  • Better runtime performance and/or
  • Retention of pre-parsed or compiled scripts (don't reparse on every run)
  • Lower or equal memory consumption
• Full ECMA-262 ECMAScript compatibility
  • a little porting can be tolerated
• Injection of custom objects into the script namespace
  • .NET objects (not a hard requirement)
  • COM objects or COM objects wrapped in .NET
• Instantiation of COM objects from Script
  • à la "new ActiveXObject(progid)"
  • Low priority given the preceeding
• Include files
  • Pre-loading of "helper scripts" into a script execution context
  • An "include" function or statement (easy to create, given the above)
• Support for code at global-scope
  • Execution of code the global scope
  • Retention of values initialized at global scope
  • Extraction of values from the global scope
  • Injection and replacement of values at the global scope
• Calling of script-defined functions
  • with parameters
  • and with access to the previously initialized global scope
• Source-level debugging
• Commercial or Open Source Support
• Non-obsolete APIs

Answer 1

Sooner or later, I imagine someone will write a DLR Javascript. I know that's not very convenient for you right now, but maybe you could start the project. I suspect it would have a better cost/benefit analysis to using JScript.NET.

Answer 2

If moving away from .NET and Microsoft is ok for you then you should try Mozilla's Rhino. It is an open-source implementation of JavaScript written entirely in Java. Alot of modern server side js libraries target this platform.

Answer 3

The use of Com interop means you are limited to an MS solution Java and Opensource want as little as possible to do with it.

I dont see any solution that supports all your requirements either you ditch all the COM/.NET stuff and go Java (Rhino) /Linux/Open source or you question the use of Javascript as your server language even in the Linux world we use PHP/Python/Ruby more on the server if we cant run Java. Your not going to see big performance gains with Java script as the language is the main barrier.

I wouldnt count on people writing a new DLR as server Java script is dying fast.

Considering you want performance ,what about F# , Microsoft will keep the Jscript engine supported for at least 5 years giving you time to create new stuff in F# while you slowly migrate the code.

Answer 4

I have used CSScript.net as it will allow you to run C# as a scripting platform. From the site:

CS-Script combines the power and richness of C# and FCL with the flexibility of a scripting system. CS-Script can be useful for system and network administrators, developers and testers. For any one who needs an automation for solving variety of programming tasks.

CS Script satisfies all the conditions that you laid out. I have used it in production as a substitute for Boo it has performed really well. You can see it in action here.

Answer 5

I answered a similar question here. Have a look at IronJS, an implementation of JavaScript in F# running on the DLR.