javascript - only new records using firebase -


i´m using firebase list of messages. problem need see messages sent after opened page. don´t need store messages in database need broadcast connected devices.

ref.limittolast(1).on('child_added', function(snapshot) {     console.log(snapshot.name(), snapshot.val()); });

the code above returns last child correctly i´m filling database messages don´t need. when right time delete "old" messages?

i don't recommend delete old messages, instead of makes every user take care of reading new.

if data structure messages working need add 1 attribute model. each time message sent add timestamp in attribute.

here doc how use servervalue.timestamp.

now every message node can ordered timestamp.

"messages": {     "chat_1": {         "push_key_usually":{          "message": "hello",          "owner": "maybe uid or email",          "chat_key": "chat_1",          "key": "push_key_usually",          "timestamp": 981212312          }     } }

to complete this, need make every user set own timestamp when load chat. way can fetch value database , order message using timestamp. complete order query value first if null first time, ask every message or work using custom timestamp (can 0 or current time minus minutes) , set value. if not null, use value query , after it, set timestamp again.

"connections": {     "user_uid": 12312412 }

now can this:

reference.child("messages/chat_1/push_key_usuarlly").orderbychild("timestamp").startat(yourtimestamp).once...

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