Escaping Characters Within RegExp Lookbehind Assertions

At Regex to match url segment only if not preceded by specific parent segment given the input http://example.com/my-slug or http://example.com/my-slug/ the requirement is to matc

Solution 1:

Since this bit of the regular expression:

[^/]+(?=\/$|$)

matches the text y-slug (y-slug is multiple non-slash characters, optionally followed by a slash, followed by the end of the string), and y-slug is not preceded by news-events/, it’s a valid match. Since my-slug doesn’t match, it’s also the first valid match, so it’s the match that is returned.

You could add a second, positive lookbehind to indicate that any match must be a complete segment.

let re = /(?<!news-events\/)(?<=\/)[^/]+(?=\/$|$)/;

let sources = [
  "http://example.com/my-slug"
, "http://example.com/my-slug/"
, "http://example.com/news-events/my-slug"
];

for (let src of sources) {
  console.log(src.match(re))
}