https://majestic.com/static/scripts/service/messaging.js?d24000

1(function() {
2    if (typeof(define) === 'function') {
3        define(['messaging'], makeService);
4    } else {
5        window.messaging = makeService();
6    }
7
8    // tokens are used to unsubscribe
9    var token = 0
10    // used to keep track of callbacks, maps channel -> token -> handler
11    var subscriptions = {}
12
13    function makeService() {
14        var messaging = {
15            send: send,
16            subscribe: subscribe,
17            unsubscribe: unsubscribe
18        };
19
20        return messaging;
21
22        // send message
23        function send(channel, message) {
24            if (subscriptions.hasOwnProperty(channel)) {
25                Object
26                    .getOwnPropertyNames(subscriptions[channel])
27                    .forEach(function (token) {
28                        subscriptions[channel][token](message);
29                    })
30            } else console.log('Message emitted, but no one was listening');
31        }
32
33        // subscribe to channel with handler
34        function subscribe(channel, handler) {
35            var thisToken = token;
36            token += 1;
37
38            if (!subscriptions.hasOwnProperty(channel)) {
39                subscriptions[channel] = {};
40            }
41            subscriptions[channel][thisToken] = handler
42
43            return thisToken;
44        }
45
46        // unsubscribe using token returned by subscribe
47        function unsubscribe(token) {
48            Object
49                .getOwnPropertyNames(subscriptions)
50                .forEach(function (channel) {
51                    if (subscriptions[channel].hasOwnProperty(token)) {
52                        delete subscriptions[channel][token];
53                    }
54                    if (Object.getOwnPropertyNames(subscriptions[channel]).length === 0) {
55                        delete subscriptions[channel];
56                    }
57                });
58        }
59    }
60})();