PubSub

This is a classic, good old publisher/subscriber utility that will let you enforce and increment heavy decoupling in your applications.

Intro

A publisher/observer central hub is a foundamental component of an application that allows dispatching messages across a channel where multiple parts of the app itself are listening or sending messages.

This allows the design to stay fully decoupled: any part A that wants to let some other part B know that something just happened, can simply throw a message in the air and if B is listening and is also interested in what happened, it will react accordingly. Otherwsie nothing will happen.

A won't have to know about B and B can be removed at any time from the app and everythig will still work. This is decoupling in its purest form and allows for scalable application of arbitary complexities.

Obviously PubSub can also be extended so that every class in the application can be made obeservable and multiple communication channels are therefore made available as a result. It is down to the developer to decide what design path to undertake.

Get an instance

const PubSub = require("pubsub_es6");

// the `new` way
var ps = new PubSub();

// or...
var ps = PubSub.singleton();  

Register callbacks

ps.subscribe("event_name", (ev, arg1, arg2) => {
   console.log(arg1, arg2);
});

// or, if you prefer your callback to be executed once only (regardless of the number of times the event is published)...
ps.once("event_name", (ev, arg1, arg2) => {
   console.log(arg1, arg2);
});

Publish events

ps.publish("event_name", "hello", "world!");

Unregister a callback

var cb = (ev, arg1, arg2) => {
   console.log(arg1, arg2);
};

ps.subscribe("event_name", cb);

// but then, later on, you change your mind.. it happens ;)
ps.unregister("event_name", cb);

// cb won't be invoked anymore
ps.publish("event_name", "hello", "world!");

Flush a whole event and its callbacks

ps.subscribe("event_name", (ev, arg1, arg2) => {
   console.log(arg1, arg2);
});

ps.once("event_name", (ev, arg1, arg2) => {
   console.log(arg1, arg2);
});

// but then, later on, you change your mind and want to reset the whole thing
ps.flush("event_name");

// no callback will be invoked
ps.publish("event_name", "hello", "world!");

Reset the whole thing

ps.subscribe("event_name_1", (ev, arg1, arg2) => {
   console.log(arg1, arg2);
});

ps.once("event_name_1", (ev, arg1, arg2) => {
   console.log(arg1, arg2);
});

ps.subscribe("event_name_2", (ev, arg1, arg2) => {
   console.log(arg1, arg2);
});

// but then, later on, you decide to reset the whole thing and flush any callback ever registered with any event
ps.reset();

// no callback will be invoked
ps.publish("event_name", "hello", "world!");

How to run Unit Tests

npm i
npm t