It's part of 2 general trends that are taking place recently. 1) A move away from server-side programming. Server is now used to serve static files and json

It's part of 2 general trends that are taking place recently. 1) A move away from server-side programming. Server is now used to serve static files and json data. Not to dynamically create pages. Application logic is not done in javascript. 2) The emergence of high-level javascript frameworks that do most of the blunt work. These frameworks are server-language agnostic and hence do all of the application scripting in browser. JQuery Mobile and Mobl come to mind here.