I know that there are lots of differences between normal web applications and desktop applications. But developing desktop applications is a lot faster than web applications, there is no needs to care about HTML, CSS, or HTTP server and database server. So developing desktop applications is much easy for most of developers. And it will also increase the speed of new products. You know speed is one of the most important factor of new web applications. So desktop applications to web applications converting is an acceptable way for web applications.
In simple, Java2Script is providing tools not libraries.