NodeJS - Creating empty array results in array with a lot of nulls
arrays, node.js, socket.io
Solution
If you have an empty array and index it with a large number (like your room id's), all slots in the array before that number are filled with `undefined` (which translates to `null` in JSON).
So try making history an object instead:
var history = {};
Problem
I am creating a Node.js chat using socket.io The problem is that when I see the `console.log` of `history` I see an array with A LOT of nulls and at the end my history entries `[null,null,null......[ { username: 'Nobody Example', message: '231', date: '03/21/2013 14:23:58' } ]]` How come these nulls are in the array? Here is a part of my code. ``` var history = []; io.sockets.on('connection', function (socket) { socket.on('send', function (message) { var date = time(); io.sockets.in(socket.room).emit('message', socket.username, message, date); history[socket.room].push({ username: socket.username, message: message, date: date }); console.log(history); }); socket.on('joinroom', function (room, username) { socket.room = room; socket.join(room); if ( typeof history[room] === 'undefined' ) history[room] = []; }); }); ``` Edit for more details: The problem is in the 'joinroom' event when creating the empty array for each room. Here are few tests that I've made: ``` socket.on('joinroom', function (room, username) { socket.room = room; socket.join(room); console.log(typeof history[room] == 'undefined'); history[room] = []; console.log(typeof history[room] == 'undefined'); console.log(JSON.stringify(history)); }); ``` The console logs: ``` true false [null,null,null,null,..................,null,[]] ```