我们如何知道环聊按钮或其他活动以获取环聊网址？

I have following code:

<script>
                gapi.hangout.render('placeholder-div', {
                  'render': 'createhangout',
                  'initial_apps': [{'app_id' : 'MY_APP_ID', 'app_type' : 'ROOM_APP' }],
                  'invites': [<?php echo $invited_emails; ?>],
                });
              </script>

But gives error like as follows:

TypeError: gapi.hangout.data is undefined
gapi.hangout.data.onStateChanged.add(function() {