There is no definitive answer to this question, since it is more related to the opinion of each one.
There you go.
Despite other languages like Typescript (Microsoft), Dart (Google) and Coffee Script, most browsers only support Javascript.
The initiative of Microsoft with the typescript language is even interesting, since the "compiler" (it is more a translator than a compiler) generates Javascript code, and therefore can be executed in any browser. The Typescript language, thus, is a super set of JS.
I've never touched on any of them, so I can not say its specific advantages, apart from the fact that Typescript compatibility does.
Today, what I have done, is to use frameworks for client code development, since there is no way to get away from JS.
What suited me best (although I'm using it in a short time), is AngularJS. It is simple, documentation is extensive (but not complete), it can be integrated with many other libraries (such as Bootstrap and jQuery) and create cool things that greatly encourage code reusability.
I also really liked Google Closure, but it's more complicated and requires a lot more from the developer than AngularJS.
Anyway, in my experience, do not run out of Javascript (at least not for the moment ...), and make use of Frameworks whenever possible.