I am not a (frontend) web developer by career. I did LAMP webdev work as a college job 12+ years ago and, like the author of this article, do small personal web projects perhaps once or twice a year. I did one of them earlier this week.
Yes, I went to Google for basic things like "Javascript map lambda" or even "Javascript foreach syntax", but I refreshed myself on those exactly once and was then able to keep it in my short term memory through the completion of the project a few days later. I switch around so many similar-but-not-identical languages (Java, Go, Python, C++, etc.) in a year that it's often not worth it for me to memorize the minutae of each one. I know how to conceptually do something in whatever language, and use search engines and stack overflow to remind myself where to put the semicolons and the brackets.