Regex to exclude words beginning with hash tag

Question

I am looking for assistance in coming up with a regular expression which will match ticket number words (any number of characters followed by digits) but not ones that begin with #SN- . Any ideas?

Example String:

A string with has ref like #SN-INC0000058 and simple mention like INC0000059.

RegEx Matches: INC0000059

I am currently stuck at this breakdown which is matching the number after '#SN-' rather than excluding the entire word/string. I suspect - is being treated as a word break... any ideas?

/(?!#SN-)([A-Z]+[0-9]+)\b/g

https://www.regexpal.com/?fam=99443

Answer 1

Since Javascript regex doesn't have the lookbehind feature, there's no way to catch what you want with a simple pattern. However, in a replacement context, you can easily handle this using a function as replacement parameter and a pattern that systematically tries to catch the part you don't want:

var result = yourstr.replace(/(#SN-)?\b[A-Z]+[0-9]+\b/g, function(m,g1) {
    return g1 ? m : 'yourreplacement';
});

When the capture group 1 is defined, the function returns the whole match, otherwise it returns the replacement string.

Note that inside the function you can't use the $& or $1..$n placeholders for the whole match or capture groups. You have to use the function parameters to figure them.

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Only to be more rigorous, it can also be done without a callback function if you describe all possibilities before your target, but it's a pain to write and it isn't efficient since the pattern starts with an alternation:

var result = yourstring.replace(/(^|[^-]|(?:[^N]|^)-|(?:[^S]|^)N-|(?:^|[^#])SN-)\b[A-Z]+[0-9]+\b/g, '$1yourreplacement');