Intl.NumberFormat
Currency formatting is in the browser, has been for years, and is still being done with a hardcoded dollar sign and a call to toFixed in most of the code I read.
AbortController
The thing everybody knows as the way to cancel a fetch is also the tidiest way to remove a pile of event listeners, and the second use has changed more of my code than the first.
Four sentences somebody could check
A client asked what progressive enhancement meant in practice and the 4 of us on the call produced about 90 seconds of gesturing, not one word of which anybody could have written down.
I wrote my own login
I spent most of last year building the login for a side project by hand on Node.js, and one Laravel command generated all of it, including the password reset I hadn't gotten to.
See email from Casey
The ugliest 40 lines on a practice's website sit under a comment telling me not to change them, and the email that comment points at stopped existing years ago.