title: Firebase push() method shuffle the list data
body: <p>Have created a chat application and we use firebase for realtime communication.
  Sometimes i noticed that push() method shuffle the list data. We can see in the below image : </p>
  
  <p><a href="https://i.stack.imgur.com/e6F7w.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/e6F7w.png" alt="enter image description here"></a></p>
  
  <p>If we see in above image i am just trying to communicate with someone i said <strong>hello</strong> in reply user said <strong>hey</strong>, again i said <strong>i need some help</strong> then user said <strong>That's what I'm here for. What can I assist you with?</strong> in the reply but if we see in the image users reply is appearing first.</p>
  
  <p>It happens intermittently that's why i didn't figure out this problem. So please someone help me out what shall i doing wrong.</p>
  
  <pre><code>var pushMessageToFB = function(){
  var chatMsgRef = db.child("chatMessages").child("gr1").child("ch_usr1_usr2");
  var message = {
      type: "chat",
      content: data.messageText,
      timestamp: Date.now(),
      by: user.id
  };
  chatMsgRef.push(message, function(err){
      if (err){
          console.log('error occurred while pushing message to fb : err ' + JSON.stringify(err));
      }
  });};
  var loadChatMessages = function(){
  var chatMsgRef = db.child('chatMessages').child("gr1").child("ch_usr1_usr2");
  $scope.chatMessages = chatMsgRef.orderByKey().limitToLast(50);  
  </code></pre>
  
  <p>};</p>