I’ll admit that it’s not something I’ve verified, just an argument I’ve seen in favour of thise practice elsewhere, but it makes sense.

If a browser already has https://code.example.com/blah.1.0.0.js in cache, wouldn’t it just use that instead of loading it again?

Edit: This post from StackOverflow lists a number of benefits, most of which will result in better perceived performance when using Google’s CDN vs hosting jQuery yourself: https://stackoverflow.com/questions/2180391/why-should-i-use...