title: Regular expression to replace digits after first 4 digits
body: <p>I am trying to write a Regular Expression that replaces all the digits of a number with *'s after first 4 digits.</p>
  
  <p>For example  </p>
  
  <pre><code>var number = 123456789  
  </code></pre>
  
  <p>it should be replaced with <code>1234*****</code></p>