on window close, not beforeunload

<apex:page showheader="false" sidebar="false">
<flow:interview name="New_Account_Wizard"></flow:interview>
<!-- New_Account_Wizard is a multi page flow with a form on each page -->
<!-- so at different stages of the flow the DOM will look different -->   
<script>

   window.onload = function () {
     var frm = document.getElementById('j_id0:j_id1:i:f');
     // do this only if the target FORM is on the curent page
     if (typeof(frm) != 'undefined' && frm != null)
     {
     
        var accountNameField = document.getElementById('j_id0:j_id1:i:f:pb:d:Company.input');
        // do this only if the target accountNameField is on the curent page
        if (typeof(accountNameField) != 'undefined' && accountNameField != null)
        {
           // Load the local Storage when the user hits the NEXT button. NEXT button does SUBMIT and goes to next page
           frm.addEventListener('submit',function(evt) {
               localStorage.setItem('AccountName', document.getElementById('j_id0:j_id1:i:f:pb:d:Company.input').value);
           });
        }
     }
     
     var finishBtn = document.getElementById('j_id0:j_id1:i:f:pb:pbb:finish');
     if (typeof(finishBtn) != 'undefined' && finishBtn != null)
     {
        // override the FINISH button on the last screen of the wizard. If you dont,
        // the natural behaviour is to restart the wizard at page one.
        finishBtn.addEventListener('click',function(evt2) {
            evt2.preventDefault();
            //console.log (document.body);
            //var list = (opener.document.body)
            
            // Remove backdrop which is covering the parent window
           // window.opener.document.getElementById("modalDivBackDrop").classList.remove("slds-backdrop--open");
            //console.log (list);

            window.close();
        });
     }
   }

    
 window.addEventListener('beforeunload', function () { 
 
    window.opener.document.getElementById("modalDivBackDrop").classList.remove("slds-backdrop--open");
    console.log('opened backdrop from popup window');
  });

</script> 
</apex:page>

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