Concurrent loading of .js files via https

Question

We're looking at splitting our .js to be served from two domains with the intent that that would enable concurrent loading.

Question: Can we a) use subdomains for that purpose and b) will that concurrent loading also hold true over https?

For instance, we'd like to request two files as such:

https://www.example.com/firstfile.js
https://subdomain.example.com/secondfile.js

Doable? Alternatives?

Answer 1

As far as I am aware, it won't work. Scripts are set up to block parallel downloads. The reason for that is that parallel loading of scripts can cause race conditions in your javascript. Minify or on demand loading are your best options.

Answer 2

I think you have to consider the latency of the network (a kind of lost time that adds up for every call to make the round trip). The latency is what kills HTTP calls responsiveness.

Personally I follow the trend to reduce the number of http calls.
I merge all my files in one (+ minimise + gzip)