How Many JavaScript Files Should a Website Have?
A maximum of four.
And I would still argue that is too many already. Considering the need for frameworks or site-wide libraries, four is the maximum I recommend.
If you have JavaScript code that only needs to run on specific pages, then there is no reason including it on other pages. Keep general JavaScript code into one and use Functional Programming to avoid repeating the same code in other external JavaScript files.
For mobile, aim for a JavaScript budget of <170KB minified/compressed. Uncompressed this is still ~0.7MB of code. Budgets are critical to success, however, they can’t magically fix performance in isolation. Team culture, structure and enforcement matter. Building without a budget invites performance regressions and failure.
[…] trim your JavaScript bundles. There’s a high chance you’re shipping full-libraries when you only need a fraction, polyfills for browsers that don’t need them, or duplicate code.
Addy Osmani
How Many CSS Files Should a Website Have?
A maximum of three.
Although I went for two for a recent SaaS, where one CSS file was a library (grids, UI, fonts) and the other one had custom styles.
Also, see what Chris Coyer thinks about this.
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