Writing client side applications in your Episerver-solutions, and creating custom localization functionality in the front end? Why not use what Episerver already has?
Episerver and ASP.NET already handles mapping host names or user context to specific languages/cultures. Why bother implementing this in the front end too?
Epinova.JsResourceHandler makes it really easy to reuse your existing localized strings in the front end. Check it out over at GitHub, where you'll also find a handy readme.
It's available in the Episerver Nuget feed.