Javascript vs c#

I just read few similar questions.
But they are all confusing me.

So, I might tell what i know and you might advice me to choose the right one.

** Can i do anything in Javascript? Or C# has more options? (Are Javascript and C# going to produce the same result with same amount of coding?)
** I read about performance issues. Is that true? Is Javascript slower than C#?

I just bought a book to read about Unity and it has Javascripts.
I know C, C++, Java and PHP (Obviously Javascript and HTML) But Javascript in web is different.

So kindly advice me to choose the right language.

Thanks

In Unity3d, both are comparable in regards to performance or features.

Use which will feel most comfortable with you, with an eye on the fact that more Unity users have provided examples in C# than in ujs.