Node.js无法读取未定义错误的属性“发出”

Question

I'm trying to send message to specific user on nodejs, then save socket.id and nickname as username into array, then get that to send message, but I get this error:

Cannot read property 'emit' of undefined

This is my code:

var socket      = require('socket.io'),
    express     = require('express'),
    app         = express(),
    server      = require('http').createServer(app),
    io          = socket.listen(server);

    io.sockets.on('connection', function (socket) {

        socket.on('login', function (data) {
            login(data.username, data.password, function (success, value) {
                if (success) {
                    usernames[data.username] = socket.id;
                    socket.emit('login', {result: true, id: value});
                } else {
                    socket.emit('login', {result: false});
                }
            });
        });

        socket.on('requestMoney', function (username) {
            log.info('username: ' + username);
            usernames[username].emit('message', {username: 'Hey !!'});
        });
    });

Answer 1

usernames[username] is undefined for the given username , because of one or more of the following things:

1. Your given username does not match a data.username connected yet, and/or
2. You're trying to call emit on an number, not a socket ( usernames[data.username] = socket.id; ), and/or
3. The usernames object is not in scope when you're trying to use it in the requestMoney event handler.

I'd like to place a wager on #2.

Answer 2

    socket.on('login', function (data) {
        login(data.username, data.password, function (success, value) {
            if (success) {
                usernames[data.username] = socket.id;
                io.sockets.emit('login', {result: true, id: value});
            } else {
                io.sockets.emit('login', {result: false});
            }
        });
    });