User Mention Regex

const pattern = /@[a-zA-Z0-9_]+/;
const text = "@username";

// Test if string matches
if (pattern.test(text)) {
  console.log("Valid!");
}

// Extract matches
const matches = text.match(pattern);
console.log(matches);

import re

pattern = r'@[a-zA-Z0-9_]+'
text = "@username"

# Test if string matches
if re.match(pattern, text):
    print("Valid!")

# Find all matches
matches = re.findall(pattern, text)
print(matches)

<?php
$pattern = '/@[a-zA-Z0-9_]+/';
$text = "@username";

// Test if string matches
if (preg_match($pattern, $text)) {
    echo "Valid!";
}

// Find all matches
preg_match_all($pattern, $text, $matches);
print_r($matches);
?>

import java.util.regex.*;

String pattern = "@[a-zA-Z0-9_]+";
String text = "@username";

Pattern p = Pattern.compile(pattern);
Matcher m = p.matcher(text);

if (m.matches()) {
    System.out.println("Valid!");
}