twemoji.js was last commited to 2 years ago, according to the Twemoji github page. I have been using the regular expression from that file in my application, to great success, but there are a lot of emojis that are not caught correctly by that regex. Examples are plenty in this tweet. Look in the tweet from the API to see the unicode character representations:
The mountain emoji is not caught by the regex.
The person emoji is caught, but on twitter.com this emoji consists of two emojis (four unicode characters), but twemoji only uses the first emoji characters, which leaves something else behind it.
The Austrian flag also consists of two emojis, and the regex catches these as two separate emojis (one saying “A”, another saying “T”).
I have been able to fix these by adding them to the regex, but it would be nice to have a more complete regex that already includes them, as well as others that have been added in the two years that twemoji.js has not been updated.