I guess he makes fun of a perceived special type of JavaScript developers: Those who were proud of their ultra-dynamic programming environment, laughing at all

I guess he makes fun of a perceived special type of JavaScript developers: Those who were proud of their ultra-dynamic programming environment, laughing at all those poor C/C++/Java folks who have to run everything through a static, rigid, stiff compiler. And now we see them doing exactly the same things there were once laughing at: They run their code through some linter/static analyzer to catch bugs early, generating their CSS with a CSS-compiler like Sass, and running their JavaScript though a minifier. Instead of a "change-test" loop now we (as JavaScript developers) have a "change-compile-test" loop, just like anyone else. It's just that we call it "build" or "minify" instead of "compile". There's some irony in that, and I believe that's what he is mocking about in that dig.