This topic was mentioned in other threads but they were either incomplete or incrorrect.

Here is the right way to add a random number to a hidden field after form is submitted.

1. 
   

   Add the following script to

   
   

    <script type="text/javascript">
   
   

   
   

   document.addEventListener(“DOMContentLoaded”, function(event) {
   
   var randomNum = ‘’;
   
   randomNum += Math.round(Math.random() * (100000 - 10000) + 10000);
   
   var elem = document.getElementById(“external_id”).value = randomNum;

   
   

   var domain = window.location.host + window.location.pathname;
   
   document.getElementById(“external_id”).value = randomNum;
   
   });

   
   

      </script>
   
   

   
   


2. 
   

   Add a hidden field in your form and give it an id name

   
   


3. 
   

   In the javascript replace the 2 instances that say “external_id” to your hidden field name

   
   

The script will generate a number between 10,000 - 100,000