It’s really unavoidable these days, and that’s good because it’s awesome. Here are some choice quotes from Kenny Meyers:
Not every company is a Ruby shop. Not every company is a .NET shop. It’s my belief that 99% of the time both of these companies will need someone who knows JavaScript, and knows it well.
When people talk about HTML5, they are talking mostly about JavaScript.
And regarding frameworks and Chicken/Eggery:
CodeIgniter certainly helped me understand PHP better. jQuery gave me a good foundation for diving deeper into JavaScript.