Defining methods via prototype vs using this in the constructor - really a performance difference?

See http://jsperf.com/prototype-vs-this

Declaring your methods via the prototype is faster, but whether or not this is relevant is debatable.

If you have a performance bottleneck in your app it is unlikely to be this, unless you happen to be instantiating 10000+ objects on every step of some arbitrary animation, for example.

If performance is a serious concern, and you'd like to micro-optimise, then I would suggest declaring via prototype. Otherwise, just use the pattern that makes most sense to you.

I'll add that, in JavaScript, there is a convention of prefixing properties that are intended to be seen as private with an underscore (e.g. _process()). Most developers will understand and avoid these properties, unless they're willing to forgo the social contract, but in that case you might as well not cater to them. What I mean to say is that: you probably don't really need true private variables...

In the new version of Chrome, this.method is about 20% faster than prototype.method, but creating new object is still slower.

If you can reuse the object instead of always creating an new one, this can be 50% - 90% faster than creating new objects. Plus the benefit of no garbage collection, which is huge:

http://jsperf.com/prototype-vs-this/59