What do you want to achieve? Run generic javascript code, or you must run your JS in IE?
If you only need to run javascript, try a JS engine, for example Google's V8. Some releated questions:
If you need to run the code in IE, that would be more tricky...
Edit: also there are multiple JS unit test runner frameworks, if that's what you are looking for. Or maybe they can be good to get some ideas.
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Then you can use the winforms WebBrowser control. Check out these on how to execute JS code in a WebBrowser control from C#: