javascript jump menu confirmation box conditional unobtrusive

<!DOCTYPE html>
<title>My Example</title>

// Put the drop down into a variable
  var e = document.getElementById("jumpmenu");
  
  // Wait for user to select an option
  e.addEventListener("change", function() {
  
      // Put the selected value into a variable
      selectedURL = this.options[this.options.selectedIndex].value;
      
      // Check that the value is not null
      if (this.value != "null") {
      
        // Display the confirm box and put the response into a variable
        var confirmLeave = confirm("Are you sure?");
        
        // If user clicked "OK"
        if (confirmLeave==true) { 
        
          // Load the selected URL
          document.location.href = selectedURL; 
        }
        // If user clicked "Cancel"
        else { 
          return false;
        }
      }     
      
  });
  
});
</script>

<form name="navForm" action="{action page}">
  <select name="jumpmenu" id="jumpmenu">
    <option>Jump to...</option>
    <option value="http://www.zappyhost.com">ZappyHost</option>
    <option value="http://www.html.am">HTML</option>
    <option value="http://www.database.guide">Database Guide</option>
  </select>
</form>