Regex for American Express Card

javascript

const regex = /^3[47][0-9]{13}$/;
const isValid = regex.test(value);

python

import re
pattern = r'^3[47][0-9]{13}$'
if re.match(pattern, value):
    print("valid")

ruby

pattern = /^3[47][0-9]{13}$/
if value =~ pattern
  puts "valid"
end

php

if (preg_match('/^3[47][0-9]{13}$/', $value)) {
    echo "valid";
}

java

String pattern = "^3[47][0-9]{13}$";
boolean isValid = value.matches(pattern);