Node.js support for => (arrow function)

The syntax you're referring to is "arrow function" syntax. It is a feature of ECMAScript 6, also known as "Harmony". The ES6 standard is now finalized, but engines are still implementing its new features.

The V8 now has arrow function support. Node runs on the V8 engine, but it can take some time for Node to incorporate the latest version into its code base.

Whenever it is added, it might possibly be enabled only via a --harmony command-line flag.

In short: yes, arrow functions are reasonably well supported in Node.js since version 4.4.5.

Completely correct support starts with version 6. Initial support was introduced as far as v0.12 but is was very incomplete and disabled by default until v4.0 when it got better. See Node's ES6 compatibility table for details: http://node.green/#ES2015-functions-arrow-functions.

You can follow this issue: https://code.google.com/p/v8/issues/detail?id=2700

Currently (as 02.05.2014) arrow functions have been implemented and waiting until this functionality will be landed in v8: https://codereview.chromium.org/160073006/

After then we'll need to wait, until v8 version with arrow function would be integrated into Node.JS. You can follow Node.JS changelog there: https://github.com/joyent/node/blob/master/ChangeLog (search for "v8: upgrade to ....")