Majority of my project is related to SharePoint. I works on SP workflow, WebParts, Event Receiver and all of SP implementation. Because of SP and other related MS product are tight to .Net language, so to speak, if you can do .Net then all of your problem in Ms stack,including SharePoint, are gone. But this rules are not applied anymore.

Back in the 2010 version, branding is not an easy task. We have to do some javascript trick to manipulate SharePoint look and feel to match its mock up. While 2013 are better in branding, new problem arise. SP now shifting to app model. Even sandbox solutions can only use client side scripting. The only use of BackEnd language is for farm solution.

Apart from SharePoint, Javascript dev is entering a heyday. Even javascript now is one of the server side language with Node. Learning it is one of the prerequisites to make cross platform app.

New style of service oriented application and Rest also emerges. New client side MVC framework like Angular also widely use even in Microsoft environment. Right now it is a common to use SharePoint as Rest provider instead of creating farm solution web part that have to be fully trust code.

So if you are a SharePoint Dev or .Net Dev, it is the time to you to learn javascript as one of your language beside C#.