Socket.io socket handles

Question

io.sockets.on('connection', function (socket) { socket.on('requestGame', function (data) { for (var game in games) if (game.player2 === undefined) { game.player2 = socket; socket.emit('gameStart', { game_id: game.game_id, turn: !p1_turn }); // works game.player2.emit('gameStart', { game_id: game.game_id, turn: !p1_turn }); // doesn't work

Why does one of these lines work while the other doesn't?

here is the error

game.player2.emit('gameStart', { game_id: game.game_id, turn: !game.p1_tur ^ TypeError: Cannot call method 'emit' of undefined

if you console.log(game.player2), what methods do you see attached to the object? — oli
– oli, Commented Jan 16, 2012 at 5:15
undefined, and if I log the socket object after that it is as expected. It's like the operation just isn't occurring. — mlihp
– mlihp, Commented Jan 16, 2012 at 5:22

fent · Accepted Answer · 2012-01-16 05:32:20Z

The for (var a in b) syntax iterates through b's keys. Each time through the loop, a will be a string, and not the value of b that you were probably looking for.

Because it's a string and a literal, attaching a property to it will immediately not have any effect on it. You cannot change literals like strings and numbers in Javascript.

'hello'.foo = 'world'; console.log('hello'.foo); // undefined var str = 'hello'; str.foo = 'world'; console.log(str.foo); // undefined

What you probably meant to do was

 for (var key in games) var game = games[key]; if (game.player2 === undefined) { game.player2 = socket; socket.emit('gameStart', { game_id: game.game_id, turn: !p1_turn }); // works game.player2.emit('gameStart', { game_id: game.game_id, turn: !p1_turn }); // doesn't work

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