How much Javascript i should know before learning Silverlight?

Question

Hi,
I haven't done any Javacripts before becauase i'm a win app developer. However i want to learn some silverlight and WPF at the moment. When i went through certain videos they talked about Javascript....
Do i need to know Javascript before learning Silverlight?
Is it possible to put a WPF componet on a webform rather than silverlight component?
TY in Advance