Graham Sutherland / Polynomialprotip: ALWAYS use regular expression literals in JavaScript and TypeScript and any other language that supports it, instead of writing your regex out in a string. I cannot count how many critical security bugs I have found over the years from someone writing a regex like "^en\.wikipedia\.org$", which is incorrect because the \. is treated as *string* escape sequence (an invalid one that just produces .) which then results in the regex being "^en.wikipedia.org$" which matches "enowikipedia.org".
I’m 481 Phones@gsuberland oh, man, I just ran into this in HTML with <input>’s pattern attribute. Nothing breaking, but even after having just read the MDN page on it, I still made this mistake and didn’t catch it until later.