title: Angular 6 email regex
body: <p>I want to validate all email inputs on my app with regex. But there is a problem, all the regex I have found allow emails with no TLD. I want a regex that can help me reject emails such as testing@testing, </p>
  
  <p>Examples: </p>
  
  <ul>
  <li>testing@testing.com should be valid</li>
  <li>testing@testing.co.us should be valid</li>
  <li>testing@testing should not be valid</li>
  </ul>
  
  <p>The current regex I use is : 
  ^([a-zA-Z0-9_-.]+)@(([[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.)|(([a-zA-Z0-9-]+.)+))([a-zA-Z]{2,4}|[0-9]{1,3})$</p>
  
  <p>But it accepts testing@testing for example, and that is not what I want.
  How would I go about validating emails and rejecting ones without TLD</p>