Javascript-TypeError：侦听器必须是一个函数

Question

Yet another 'listener must be a function' error. I double checked all my parameters, checked for correct syntax etc but still can't find where the problem is:

Here are my snippets of code.

in login.js:

global.eventEmitter = require('./helpers/EventEmitter.js');
var packetSwitch = require('./handlers/PacketSwitch.js');
global.ackHandler = require('./handlers/ACKPacketHandler.js');
...
global.eventEmitter.createAndFireEvent('opCodeReceived',packetSwitch.switch(opcode, decrypted, sock));

in PacketSwitch.js:

var packetHandler = require('./PacketHandler.js');
exports.switch = function(opcode, data, sock) {
    switch (opcode) {
        case 1:
            eventEmitter.createAndFireEvent('reqLoginReceived', packetHandler.handleLoginReq(data, sock));
            break;
        case 2:
            eventEmitter.createAndFireEvent('reqDateReceived', packetHandler.handleDateReq(data, sock));
            break;
        default:
            eventEmitter.createAndFireEvent('unknownReceived', packetHandler.handleUnknown(data, sock));
    }
};

let's suppose it enters case 2: in PacketHandler.js:

exports.handleDateReq = function(data, sock) {
    global.eventEmitter.createAndFireEvent('handleDateAck', global.ackHandler.handleDateAck(sock));
};

in ACKPacketHandler.js:

exports.handleDateAck = function(sock) {
    sock.write("Test!");
};

in EventEmitter.js:

var eventEmitter = require('events');
const myEmitter = new eventEmitter.EventEmitter();

exports.createAndFireEvent = function(event, callback) {
    myEmitter.on(event, callback);
    myEmitter.emit(event);
};

And here's a screenshot of the error I get: https://gyazo.com/6047c5917f937aa33f29f9fc40cdf5f7

Answer 1

Your packet handler functions (eg handleDateAck() ) are not returning functions. In fact, they don't seem to be returning anything. The return value is what you're currently using as the listener function passed to emitter.on() .