Page 144 - JavaScript

var jane = new Employee('Jane');
var meetingAlerts = new Subject();
meetingAlerts.registerObserver(bob);
meetingAlerts.registerObserver(jane);
meetingAlerts.notifyObservers('4pm');

// Output:
// Bob: There is a meeting at 4pm
// Jane: There is a meeting at 4pm

Mediator Pattern

Think of the mediator pattern as the flight control tower that controls planes in the air: it directs this
plane to land now, the second to wait, and the third to take off, etc. However no plane is ever
allowed to talk to its peers.

This is how mediator works, it works as a communication hub among different modules, this way
you reduce module dependency on each other, increase loose coupling, and consequently
portability.

This Chatroom example explains how mediator patterns works:

// each participant is just a module that wants to talk to other modules(other participants)
var Participant = function(name) {
this.name = name;
this.chatroom = null;
};
// each participant has method for talking, and also listening to other participants
Participant.prototype = {
send: function(message, to) {
this.chatroom.send(message, this, to);
},
receive: function(message, from) {
log.add(from.name + " to " + this.name + ": " + message);
}
};

// chatroom is the Mediator: it is the hub where participants send messages to, and receive
messages from
var Chatroom = function() {
var participants = {};

return {

register: function(participant) {
participants[participant.name] = participant;
participant.chatroom = this;
},

send: function(message, from) {
for (key in participants) {
if (participants[key] !== from) {//you cant message yourself !
participants[key].receive(message, from);
}
}
}

https://riptutorial.com/ 101