[pritambaral]

Pardon me if I read it wrong, but you just removed the promises, didn't you?

Anyway, doing the same to the FP version yields almost equal speeds (Chromium):

http://jsperf.com/oop-vs-fp

[idlewan]

I removed all the useless promises, yes.

The one remaining is the one after fetchData, which looks like it could be async and make use of a promise.

It only yields equal speeds in chromium (good to know), although if you try in firefox, imperative is still 4 times faster.