30k of JavasScript isn't that much

This week, I was exchanging emails with someone around using frameworks to handle rendering.

I mentioned that, for certain types of apps, I like them, but prefer to use smaller libraries like Reef over the extra bloat that 30kb of JS framework brings.

They responded:

I don’t get the “bloat” argument. 30kb isn’t that much.

And to be fair, it’s not.

30kb is small relative to your computer’s overall storage space. A 30kb JPG is tiny. It’s a trivial amount of data to send on a fast internet connection.

That said…

A good amount of web traffic is now mobile, and a good amount of mobile web access is on midrange smart phones with ok-ish/flaky/bad internet connections.

JavaScript is a very different beast than a JPG, or even CSS.

It blocks rendering, and it blocks other files from downloading. It needs to parsed and interpreted after it’s downloaded, and triggers a bunch of repaints that negatively affect performance. Byte-for-byte, JS is the single most expensive resource we send down the wire.

So, 30kb isn’t a lot in the absolute sense, but in terms of a performance budget, 30kb of JS is orders of magnitude more impactful than the same amount of any other file type.