pubhop

A library that simplifies the pub-sub model for TypeScript and JavaScript.

Installation

npm install pubhop

Usage

This package exports several useful classes, each of which has a specific use-case.

When you need to handle a bare-bones publisher-subscriber model, which doesn't maintain any state, you should use Publisher:

import { Publisher } from "pubhop";

type Person = {
  name: string;
  age: number;
};

const publisher = new Publisher<(person: Person) => void>();

const unsub = publisher.subscribe((person) => {
  // this will be called whenever `publisher.publish` is called
});

publisher.publish({ name: "Evyatar", age: 19 });

unsub();

// from here on out, `publisher.publish` will no longer trigger our subscriber

If you have multiple publishers, you can handle them with a Network:

import { Network } from "pubhop";

type Person = {
  name: string;
  age: number;
};

type BlogEvents = {
  newReader: (latest: Person, readers: Person[]) => void;
  like: (count: number) => void;
};

const network = new Network<BlogEvents>(); // we now essentially have "newReader" and "like" publishers

const unsub = network.subscribe("newReader", (latest, readers) => {
  // this will be called whenever "newReader" is published to
});

const unfollow = network.follow((...data) => {
  // this will be called whenever `publish` is called, no matter for what key
});

network.publish("newReader", { name: "Evyatar", age: 19 }, [{ name: "Evyatar", age: 19 }]);

// and as with `publisher`, we can use the returned functions to unsubscribe/unfollow
unsub();
unfollow();

When you also need to manage some sort of state, you should use a Store:

import { Store } from "pubhop";

type Person = {
  name: string;
  age: number;
};

const store = new Store<Person>({ name: "Evyatar", age: 19 }); // we can pass initial values to a store, unlike a publisher

// we can subscribe just like with a publisher
const unsub = store.subscribe((person) => {
  // this will be called whenever the store is updated
});

// however, stores also maintain state
// which we can set, calling all subscribers with the new value
store.set({ name: "Joe", age: 27 });

// and which we can get
const person = store.get();

// and as always, when we subscribe we can unsubscribe
unsub();

Finally, if you have multiple stores, you can handle them with a Client:

import { Client } from "pubhop";

type Person = {
  name: string;
  age: number;
};

type BlogInfo = {
  readers: Person[];
  latestReader: Person;
  likes: number;
};

const client = new Client<BlogInfo>(); // we now essentially have "readers", "latestReader", and "likes" stores

// we can subscribe to a specific store
const unsub = client.subscribe("latestReader", (person) => {
  // this will be called whenever the "latestReader" store is updated
});

// or follow all of them
const unfollow = client.follow((data) => {
  // this will be called whenever any store is updated
});

client.set("likes", 10);
client.set("readers", [{ name: "Evyatar", age: 19 }]);

// data, just like a store's, can be retrieved using `get`
const likes = client.get("likes");

// and as always, when we subscribe we can unsubscribe
unsub();
unfollow();

API

Publisher

A Publisher maintains a list of subscribers which it notifies of any publishes. It does not manage any internal state about the data that has been published, but simply passes the data along to its subscribers.

The Publisher class has one generic type argument, TSub, which is the type of the subscriber functions. TSub must be a function that returns void.

class Publisher<TSub extends (...args: any) => void>;

Publisher.subscribe

Publisher<TSub>.subscribe(cb: TSub): () => void;

Adds a new subscriber to the publisher.

Takes a cb parameter, which will be called on every publish.

Returns an unsubscribe function, which removes the function from the list of subscribers.

Publisher.publish

Publisher<TSub>.publish(...params: Parameters<TSub>): void;

Notifies all subscribers with the specified data.

Takes params, which are passed to each of Publisher's subscribers, in insertion order.

Publisher.clear

Publisher<TSub>.clear(): void;

Removes all subscribers from the publisher.

Store

A Store maintains a list of subscribers just like a Publisher, but also manages an internal state. This state is the determiner of when and with what to notify the subscribers.

The Store class has one generic type argument, TData, which is the type of the internal state and the parameter for the subscriber functions.

class Store<TData>;

Store() constructor

new Store<TData>(initialValue?: TData);

Store can be initialized with a value, or be left empty.

Store.get

Store<TData>.get(): TData | undefined;

Gets a snapshot of the store's state.

Returns TData if the store was initialized with data or has had its data set, and undefined otherwise.

Store.set

Store<TData>.set(data: TData): void;

Updates the store's state, and notifies all subscribers.

Takes a data parameter, which will be inserted into the store's state (accessed by get), and which all subscribers will be called with.

Store.subscribe

Store<TData>.subscribe(cb: (data: TData) => void): () => void;

Adds a new subscriber to the store.

Takes a cb parameter, which will be called on every set.

Returns an unsubscribe function, which removes the function from the list of subscribers.

Network

A Network maintains as a collection of subscribers, each listening for a specific "event", along with a collection of followers, which listen for every update that the network provides. It does not manage any internal state about the data that has been published, but simply passes the data along to its subscribers and followers.

The Network class has one generic type argument, THandlers. Each key of THandlers signifies an event "name" or "key", while each value (which must all be functions that return void) signifies the types of that event's subscribers.

class Network<THandlers extends Record<PropertyKey, (...args: any) => void>>;

Network.subscribe

Network<THandlers>.subscribe<TEvent extends keyof THandlers>(
    event: TEvent,
    cb: THandlers[TEvent]
): () => void;

Adds a new subscriber to a specific event within the network.

Takes an event parameter, which specifies which of the network's events to listen for. Takes a cb parameter, which will be called on every publish to event.

Returns an unsubscribe function, which removes the function from the list of subscribers.

Network.publish

Network<THandlers>.publish<TEvent extends keyof THandlers>(
    event: TEvent,
    ...args: Parameters<THandlers[TEvent]>,
): void;

Notifies all subscribers of a specific event, along with all of the network's followers, with the specified data.

Takes an event parameter, which specifies which event's subscribers should be notified. Takes params, which are passed to each of event's' subscribers and all of the network's followers, in insertion order.

Network.follow

// it should be noted that this type signature is an oversimplification;
// `Network` uses a mapped type to ensure that `event` and `...data` are always synced up.
Network<THandlers>.follow(cb: (event: keyof THandlers, ...data: THandlers[typeof event])): () => void

Adds a follower to the network, which is notified of every publish, regardless of key.

Takes a cb parameter, which will be called with the event's name and the associated data on every publish.

Returns an unfollow function, which removes the function from the list of followers.

Network.clear

Network<THandlers>.clear(event: keyof THandlers): void;

Removes all subscribers for a specific event.

Takes an event parameter, which determines which subscribers to remove.

Network.fullClear

Network<THandlers>.fullClear(): void;

Remove all subscribers and all followers of the network, regardless of events.

Client

A Client maintains as a collection of stores and their subscribers, along with a collection of followers which listen for updates on every store.

The Client class has one generic type argument, TData. Each key of TData signifies a store's key, while each value signifies the data within that store.

class Client<TData extends Record<PropertyKey, any>>;

Client() constructor

new Client<TData>(initialValues?: Partial<TData>);

Client can be left empty, or have any of its stores initialized.

Client.get

Client<TData>.get<TKey extends keyof TData>(key: TKey): TData[TKey];

Gets a snapshot of a specific store's state.

Takes a key parameter which specifies which store to get the data from.

Returns TData[TKey] if that store was initialized with data or has had its data set, and undefined otherwise.

Client.set

Client<TData>.set<TKey extends keyof TData>(
    key: TKey,
    data: TData[TKey]
): void;

Updates a specific store's state, and notifies all of its subscribers.

Takes a key parameter, which specifies which store should have its data updated and its subscribers notified. Takes a data parameter, which will be inserted into that store's state, and which all of its subscribers will be called with.

Client.subscribe

Client<TData>.subscribe<TKey extends keyof TData>(
    key: TKey,
    cb: (data: TData[TKey]) => void
): () => void;

Adds a new subscriber to a specific store.

Takes a key parameter, which specifies which store's updates to listen for. Takes a cb parameter, which will be called on every set to that store.

Returns an unsubscribe function, which removes the function from the list of subscribers.

Client.follow

// it should be noted that this type signature is an oversimplification;
// `Client` uses a mapped type to ensure that `key` and `data` are always synced up.
Client<TData>.follow(cb: (key: keyof TData, data: TData[keyof TData])): () => void;

Adds a follower to the client, which is notified of every set, regardless of key.

Takes a cb parameter, which will be called with the key and the associated data on every set.

Returns an unfollow function, which removes the function from the list of followers.

TypedMap

A wrapper for JavaScript's Map object that allows strong typing. Used internally by Network and Client.

The TypedMap class has one generic type argument, TData, which signifies the key-value pairs of the map.

TypedMap has the same API as Map, only with stronger types.