Node.js crash - async issue or something else? - arrays

Question

I've got a crash happening on my node server and I can't figure out how it could logically happen. I haven't personally repro'd but its happened a few times in the last week according to bugsnag. Any thoughts on why it might be happening or suggestions for additional logging to help debug would be greatly appreciated.
I've got a 2-player game, where each person is dealt a hand, and then needs to select two cards from their hand to discard. Discarding is done simultaneously, so players may discard at different moments or the same moment. Here's my discard function:
Game.prototype.discard = function(socket, msg) {
var self = this;
socket.get('playerNum', function (err, playerNum) {
self.crib.push(self.cards[playerNum].splice(msg.cards[0],1)[0]);
self.crib.push(self.cards[playerNum].splice(msg.cards[1]-1,1)[0]);
for (var i = 0; i < self.cards[playerNum].length; i++) //add cards kept as unpegged
self.currentUnPeggedCards.push(self.cards[playerNum][i]);
socket.broadcast.in('gamea' + self.tableNumber).emit('other player discarded');
if (self.crib.length == CARDS_PER_CRIB) { //both players discarded
var jsonGame = self.buildJSON('starter');
self.dbConnection.query("UPDATE savedgames SET game = '"+jsonGame+"' WHERE room = 'a' and player1_id = "+self.seatedPlayers[0][2]+" and player2_id = "+self.seatedPlayers[1][2]+";");
if (playerNum == self.dealer)
socket.broadcast.in('gamea' + self.tableNumber).emit('cut starter card');
else
socket.emit('cut starter card');
}
else {
var jsonGame = self.buildJSON('discard');
self.dbConnection.query("UPDATE savedgames SET game = '"+jsonGame+"' WHERE room = 'a' and player1_id = "+self.seatedPlayers[0][2]+" and player2_id = "+self.seatedPlayers[1][2]+";");
}
});
}
The msg param is passed in from the client side, and is built as the result of the user toggling two cards and then selecting to discard. Here's what the client-side code generating the msg looks like:
function clickedDiscard() {
if (myTurnButton) {
var discards = [];
var keepCards = [];
for (var i=0; i<6; i++) {
if (cardsClicked[i])
discards.push(i);
cardsClicked[i] = false;
}
numCardsClicked = 0;
socket.emit('discard',{cards:discards});
}
}
So it pushes two cards to self.crib (which contains both player's discards), then it checks to see if both players have discarded (by looking at the length of self.crib, and then I'm building a storing a json object which represents the current state of the game, so if people get disconnected they can resume, etc.
The crash is happening in my buildJSON function. Here's the entire code for that function (as requested):
Game.prototype.buildJSON = function(state) {
console.log('starting build json');
var self = this;
var stateStr = '"state":"'+state+'",';
var scoreStr = '"score":['+self.score+'],';
var winsStr = '"wins":['+self.wins+'],';
var mostRecentPtsStr = '"mostRecentPts":['+self.mostRecentPts+'],';
var mostRecentCardPtsStr = '"mostRecentCardPts":['+self.mostRecentCardPts+'],';
var mostRecentCountStr = '"mostRecentCount":['+self.mostRecentCount+'],';
var dealerStr = '"dealer":'+self.dealer+',';
var dealsFirstStr = '"dealsFirst":'+self.dealsFirst+',';
var peggerStr = '"pegger":'+self.currentPegger+',';
var cardNamesStr = '"hands":[';
for (var i=0; i<self.cards.length;i++) {
cardNamesStr += '[';
for (var j=0; j<self.cards[i].length;j++) {
cardNamesStr += '"'+self.cards[i][j].getName()+'"';
if (j==self.cards[i].length-1)
cardNamesStr += ']';
else
cardNamesStr += ',';
}
if (i!=self.cards.length-1)
cardNamesStr += ',';
}
cardNamesStr += '],';
var cribStr = '"crib":[';
for (var i=0;i<self.crib.length;i++) {
cribStr += '"'+self.crib[i].getName()+'"';
if (i!=self.crib.length-1)
cribStr += ',';
}
cribStr += '],';
var starterStr = '';
if (self.starterCard != null)
starterStr = '"starter":"'+self.starterCard.getName()+'",';
var deckStr = '"deck":[';
var deckCards = self.deck.getCards();
for (var i=0;i< deckCards.length;i++) {
deckStr += '"'+deckCards[i].getName()+'"';
if (i!= deckCards.length-1)
deckStr += ',';
}
deckStr += '],';
var pegCountStr = '"count":'+self.currentPeggingCount+',';
var peggedStr = '"pegged":[';
for (var i=0; i<self.peggedCards.length;i++) {
peggedStr += '[';
for (var j=0; j<self.peggedCards[i].length;j++) {
peggedStr += '"'+self.peggedCards[i][j].getName()+'"';
if (j!=self.peggedCards[i].length-1)
peggedStr += ',';
}
peggedStr += ']';
if (i!=self.peggedCards.length-1)
peggedStr += ',';
}
peggedStr += '],';
var currentPeggedStr = '"currentPegged":[';
for (var i=0;i<self.currentPeggedCards.length;i++) {
currentPeggedStr += '"'+self.currentPeggedCards[i].getName()+'"';
if (i!=self.currentPeggedCards.length-1)
currentPeggedStr += ',';
}
currentPeggedStr += '],';
var currentUnPeggedStr = '"currentUnPegged":[';
for (var i=0;i<self.currentUnPeggedCards.length;i++) {
currentUnPeggedStr += '"'+self.currentUnPeggedCards[i].getName()+'"';
if (i!=self.currentUnPeggedCards.length-1)
currentUnPeggedStr += ',';
}
currentUnPeggedStr += ']';
var gameJSON = '{' + stateStr + scoreStr + winsStr + mostRecentPtsStr + mostRecentCardPtsStr + mostRecentCountStr + dealerStr + dealsFirstStr + peggerStr + cardNamesStr + cribStr + starterStr + deckStr + pegCountStr + peggedStr + currentPeggedStr + currentUnPeggedStr + '}';
console.log('json built');
return gameJSON;
}
The crash happens on the call to getName(), with the error being: Cannot call method 'getName' of undefined
At this point, I'm not sure how this can happen. The for loop, is, by definition over the length of the object, so there has to be an element at each index in the loop. And yet, clearly there isn't, because the object is undefined. Is this somehow happening because of an async problem? When pushing to an array, does it somehow increase the length of the array before actually adding the object to the array itself? I suppose it's possible that what I'm splicing out of the original array is undefined? Pretty stumped.