title: Format number string using commas
body: <p>I want to format numbers. I have seen some of the regex expression example to insert comma in number string. All of them check 3 digits in a row and then insert comma in number. But i want something like this:</p>
  
  <pre><code>122 as 122
  1234 as 1,234
  12345 as 12,345
  1723456 as 17,23,456
  7123456789.56742 as 7,12,34,56,789.56742
  </code></pre>
  
  <p>I am very new to regex expression. Please help me how to display the number as the above. I have tried the below method. This always checks for 3 digits and then add comma.</p>
  
  <pre><code>function numberWithCommas(x) {
      return x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
  }
  </code></pre>
  
  <p>But i want comma every 2 digits except for the last 3 digits before the decimals as shown above.</p>