title: How to validate url?
body: <p>I want to validate urls.
  It should accept:</p>
  
  <pre><code>http://google.com
  
  http://www.google.com
  
  www.google.com
  
  google.com
  </code></pre>
  
  <p>I refer <a href="https://stackoverflow.com/questions/1141848/regex-to-match-url">Regex to match URL</a> .</p>
  
  <p>But it is not supporting <code>google.com</code> . </p>