Regex returns no match in Dart but works in online regex testers

Question

I have built a regex which should match valid HTTP headers. It works, sort of, on regexr: https://regexr.com/4pnk9, with regex ^([\\w\\-])+:(?!\\s*$).+$. I am using

Answer 1

You may either use

r"^([\w-])+:(?!\s*$).+$"

or

"^([\\w-])+:(?!\\s*\$).+\$"

Note that inside a non-raw string literal, the double backslashes stand for a single literal backslash. In a raw string literal, you do not need to escape the $ symbol and you only need a single backslash to form a regex escape.