In the Array.prototype.at() MDN Web Docs, the Browser Compatability for Safari is listed as 'TP' in a blue square. What does TP mean?
Taken from here: https://github.com/mdn/browser-compat-data/blob/main/javascript/builtins/Array.json
It says preview for Safari, and no support for Safari iOS.
TP stands for "Technology Preview", an experimental version of Apple's Safari browser. On the mdn page, there is an abbr tag next to TP with a title of "Preview browser support".