Regular Expression to match #hashtag but not #hashtag; (with semicolon)

问题

I have the current regular expression:

/(?<=[\s>]|^)#(\w*[A-Za-z_]+\w*)/g

Which I'm testing against the string:

Here's a #hashtag and here is #not_a_tag; which should be different. Also testing: Mid#hash. #123 #!@£ and <p>#hash</p>

For my purposes there should only be two hashtags detected in this string. I'm wondering how to alter the expression such that it doesn't match hashtags that end with a ; in my example this is #not_a_tag;

Cheers.

回答1:

How about the following:

\B(\#[a-zA-Z]+\b)(?!;)

Regex Demo

\B -> Not a word boundary
(#[a-zA-Z]+\b) -> Capturing Group beginning with # followed by any number of a-z or A-Z with a word boundary at the end
(?!;) -> Not followed by ;

回答2:

You can use a negative lookahead reegex:

/(?<=[\s>]|^)#(\w*[A-Za-z_]+\w*)\b(?!;)/

\b - word boundary ensures that we are at end of word
(?!;) - asserts that we don't have semi-colon at next position

RegEx Demo

回答3:

Similar to anubhava's answer but swap the 2 instances of \w* with \d* as the only difference between \w and [A-Za-z_] is the 0-9 characters

This has the effect of reducing the number of steps from 588 to 90

(?<=[\s>])#(\d*[A-Za-z_]+\d*)\b(?!;)

Regex101 demo

回答4:

/(#(?:[^\x00-\x7F]|\w)+)/g

Starts with #, then at least one (+) ANCII symbols ([^\x00-\x7F], range excluding non-ANCII symbols) or word symbol (\w).

This one should cover cases including ANCII symbols like "#їжак".

回答5:

This is the best practice.

(#+[a-zA-Z0-9(_)]{1,})

来源：https://stackoverflow.com/questions/38506598/regular-expression-to-match-hashtag-but-not-hashtag-with-semicolon

标签

regex

hashtag