title: Angular2/4 Telephone Validation
body: <p>I am trying to implement a form in Angular 2/4. There is a field for Telephone number. I used a regular expression as </p>
  
  <pre><code>pattern="^\s*(?:\+?(\d{1,3}))?[- (]*(\d{3})[- )]*(\d{3})[- ]*(\d{4})(?: *[x/#]{1}(\d+))?\s*$"
  </code></pre>
  
  <p>in the corresponding input field. It accepts almost all the formats but not the following:</p>
  
  <ol>
  <li><p>754-3010 (Local)</p></li>
  <li><p>(541) 754-3010 (Domestic)</p></li>
  <li><p>+1-541-754-3010 (international)</p></li>
  </ol>
  
  <p>More over it should accept +, -, (, and ) characters.</p>
  
  <p>Hope some one can help </p>