title: Mask US phone number string with JavaScript
body: <p>I need regular express for US Phone Number format.I want to replace the phone number string into below US phone number string format in JavaScript.</p>
  
  <pre><code>var number = "4031234789";
  </code></pre>
  
  <p>And I want to mask it in below format:-</p>
  
  <pre><code>number = number.mask('(000) 000-0000');
  </code></pre>
  
  <p>Can anyone show me a regular expression for that in JavaScript?</p>