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The differences between observer, pubsub, and mediator pattern

Understanding the basic differences between the 3 patterns.

Observer: the publisher must know and manage observers, observers will be attached to the specific publisher:

const observer = function(data) {
   console.log('received event');
};
Publisher.addObserver(observer);
Publisher.notify('data');

Pubsub: the publisher can publish an event without knowing who are the listeners, publisher and listeners communicate through the event channel:

const subscriber = function(data) {
    console.log('received event');
};
Pubsub.on('event', subscriber);
// Publisher publishes event through Pubsub object
Pubsub.publish('event', 'data');

Mediator: groups logic of domain that has indirect relationship between modules. We can use Pubsub (not required, can use other patterns) to manage the workflow :

const Mediator = {
    init: function() {
        Pubsub.on('event', doSomething.bind(this));
    },
    doSomething: function(data) {
        // do other actions, like calling Ajax and notifying another event.
        Ajax.get('path', data)
        .then(function(res) {
            Pubsub.publish('another event', res);
        });
    }
};
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