Scalable real-time backend

var messagesRef = new Firebase('https://chat.firebaseIO.com/');

// Write messages.
messagesRef.push({name:"Alice",text:"Firebase is awesome!"});

// Read messages.
messagesRef.on("child_added", function(message) {
  renderMessage(message.val());
});

// Write a pixel.
$(myCanvas).mousemove(function(e) {
  var x1 = Math.floor((e.pageX - offset.left) / pixSize - 1);
  var y1 = Math.floor((e.pageY - offset.top) / pixSize - 1);
  pixelDataRef.child(x0 + ':' + y0).set(currentColor);
}
// Render a pixel.
pixelDataRef.on('child_added', drawPixel);

// Query the 10 highest scores.
var scoreListView = scoreListRef.limit(10);

// Add callbacks to update the gui when scores change.
scoreListView.on('child_added', handleScoreAdded);
scoreListView.on('child_removed', handleScoreRemoved);
scoreListView.on('child_moved', changedCallback);

// Watch for changes to the current piece.
pieceRef.on('value', function(snapshot) {
  if (snapshot.val() === null) {
    var newPiece = new Tetris.Piece();
    newPiece.writeToFirebase(pieceRef);
  } else {
    self.fallingPiece = Tetris.Piece.fromSnapshot(snapshot);
  }
});

// When a connection is established, mark myself online.
ref.child('.info/connected').on('value', function(isOnline) {
  if (isOnline.val()) {
    // Update my state if I go offline.
    myUserRef.onDisconnect().remove();
    myUserRef.set('Online');
  }
});