As a developer with very strong roots in .NET and especially C# I was very excited when Microsoft brought Silverlight (first versions where called Windows Presentation Foundation/Everywhere) to the market.
This could be the cool feature which made it possible to run code crossplatform as you could do more or less with Java.

Unfortunately it didn't become as popular as expected because browserplugins where more and more banned from several browsers, starting with Safari and iOS. This meant you couldn't (and still can't) run Silverlight or Flash on your brand new and hip iPad or iPhone.

HTML5 and Javascript to the rescue. You can create equally stunning webapplication and userexperiences with this new technology and it will run on all kinds of browsers on basically all platforms. So I jumped onto this new and exciting technology in late 2010 and started training other developers in early 2011.

While looking for a solution to use in my training for websockets (which where very unstable and experimental then) when I got introduced to nodejs.
A very easy way to run very responsive applications and have full control. And it was written in a language I already mastered: Javascript!

Cool! Now I could demo all HTML5 stuff including websockets in just one language.

Not much later I started investigating mobile webapps and build my first demos with Phonegap and Sencha touch. And so I could also create mobile apps with Javascript (and some HTML5 of course).

And in fall 2013 I started to play with a new toy called node-webkit, a very nice tool in which you can build desktop applications for MacOSX, Windows & Linux. Combining the strength of nodejs and chromium.

So now you can create applications with HTML5 and Javascript in your browser, on the server with nodejs, on mobile devices with Phonegap or Sencha Touch and desktop applications with node-webkit. It looks like Javascript is the first programming language to become really platform independent and with a very wide reach today.