JavaScript appendChild Not Posting to Form

I was battling an issue where  I was using the following function to add a field to a form:

function addRow (tblID){
   var tblBody = document.getElementById(tblID).tBodies[0];
   len = tblBody.rows.length;
   var newNode = tblBody.rows[len-1].cloneNode(true);
   tblBody.appendChild(newNode);
 }

All the fields that were being appending were not being included on the form post, but any field I manually put in the code would post. After battling it for far too long I moved the opening and close form tags to the end and close of the file and everything worked correctly. I’m not sure why the form location worked with a hardcoded input but not with one that was manually input, but moving the form tag was easy enough.