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Holmström has already tested his implementation against a similar project called Jint. Both projects are implementations for the .NET Common Language Runtime, but only IronJS runs on the DLR. The benchmarks recorded set variable performance, function call performance, and member access performance. IronJS was significantly faster than Jint in all of Holmström's tests: it was 3 times faster in member access performance, 6 times faster in set variable performance, and about 11 times faster in function call performance. Holmström has also posted a recent unit test showing that IronJS now compiles jQuery 1.4:
1) Free and Open Source
2) Actively developed
After searching for almost two months for a suitable JS runtime I simply realized that if I wanted it I'd have to do it myself. I started working on IronJS in the beginning of January this year, so a bit more than three weeks have passed since I wrote the first line on what was to become IronJS."
"My vision is to create an ECMA Script 5.0 (the current goal is ECMA Script 3.0, though) compliant implementation, that is open and free," said Holmström. "I also want to work with, or at least follow the progress of, the CommonJS initiative, and if it takes off (as I think we all hope it will) I want to provide an implementation of those libraries for IronJS as well. As I said, I have two other projects relying on IronJS as a script runtime that are heavily tied to web development - I'm not ready to expose them to the public yet though - IronJS is an important part of making these two projects work also."
Iron JS is licensed under the GNU General Public License v3. It requires .NET 4.0 Beta 2, since a few C# 4.0 specific features, like covariance, are used.