Regex (JS)：匹配没有协议的URLs，忽略有协议的URLS

/^(?!https?:\/\/)(?:\w+\.)+\w+(?:\/\S*)?$/

const regex = /^(?!https?:\/\/)(?:\w+\.)+\w+(?:\/\S*)?$/;

const urls = [
  'example.com',
  'http://example.com',
  'https://example.com',
  'subdomain.example.com',
  'http://subdomain.example.com',
  'https://subdomain.example.com',
  'example.com/path',
  'http://example.com/path',
  'https://example.com/path',
  'subdomain.example.com/path',
  'http://subdomain.example.com/path',
  'https://subdomain.example.com/path'
];

urls.forEach(url => {
  if (regex.test(url)) {
    console.log(`${url} 匹配成功`);
  } else {
    console.log(`${url} 匹配失败`);
  }
});

example.com 匹配成功
http://example.com 匹配失败
https://example.com 匹配失败
subdomain.example.com 匹配成功
http://subdomain.example.com 匹配失败
https://subdomain.example.com 匹配失败
example.com/path 匹配成功
http://example.com/path 匹配失败
https://example.com/path 匹配失败
subdomain.example.com/path 匹配成功
http://subdomain.example.com/path 匹配失败
https://subdomain.example.com/path 匹配失败