Here are Few -
Homogenous Programming Experience
With server-side JavaScript (SSJS) you can use the same language on the server, on the client and over the wire (JSON). JavaScript is even deeply integrated into a number of database platforms. This lowers the concept count for web development and reduces the need for context switching.
JavaScript Runtime Engines
There is a large and ever expanding list of quality, cross-platform JavaScript engines. Every browser contains a JS runtime and there is currently a gold rush on JS performance improvements.
Performance
If you have ever seen IE6 I know you will have your doubts, but JavaScript is fast. Not fast relative to C, but fast relative to languages with comparable features, and it is getting faster.
Interpreted Language
You are too old for training wheels, and programming is too old for a compilation step. Now that we know the benefits of agile, and TDD, and rapid feedback loops, an interpreted language is a big advantage.
CommonJS
JavaScript has traditionally been confined to the browser and supported by an extremely limited library. To address this issue in a standard way the CommonJS specification was created to define a common set of JavaScript libraries.
