Visual Studio 2008和覆盖现有文件扩展名的LanguageService

I write simple LanguageService for JavaScript language. Target IDE is Visual Studio 2008. I want to run my LanguageService for .js extension file(default extension for JavaScript language). But for this extension my LanguageService don't working. When I run my LanguageService for extension .jsp(could be any extension don't supporting by VS IDE) - LanguageService working well.I write simple LanguageService for JavaScript l