pusu

Simple type-safe pub-sub implementation APIs for Javascript/TypeScript Apps

Create Publication

type TCreateConfiguration = {
  name?: string;
  enableLogging?: string;
};

type TPublication<T> = {
  config?: TCreateConfiguration,
  subscribers: ((data: T) => void)[],
}

declare const createPublication: <T>(config?: TCreateConfiguration | undefined) => TPublication<T>;

Parameters:

• config: (Optional) TCreateConfiguration - Configuration options.

Return value: Object - New publication.

Creates & returns a unique new publication object.

Configuration

• name?: (Optional) string - Used in logging. Default: "Unknown".
• enableLogging?: (Optional) boolean - Enable/disable console logging. Useful in development and/or test environments. If enabled then each action "create" | "publish" | "subscribe" | "unsubscribe" | "notify" gets logged on console with relevent data.

Example

import { createPublication } from 'pusu';

export default createPublication<{ asOfDate: Date }>({ name: 'load-data' });

Unique publication every time

Creation of a publication makes sure that each publication is unique in itself and removes the need of maintaining a unique key for each publication.

Even if multiple publications created with same name, then each publication will be treated as a separate publication without any conflicts.

Below code creates two separate unique publications publication1 & publication2 even though the publication names are same. Name is just for the sake of naming the publication so that its useful during debugging any issues.

Example

import { createPublication } from 'pusu';

const publication1 = createPublication<{ asOfDate: Date }>({ name: 'load-data' });
const publication2 = createPublication<{ asOfDate: Date }>({ name: 'load-data' });

console.log(publication1 === publication2); //false

Publish

declare const publish: <T>(publication: TPublication<T>, data: T) => void;

Parameters:

• publication: (Required) Object - Publication object created using the api createPublication()
• data: (Optional) - This argument is passed to the subscribers listening to the publication. Its a way of passing data to the subscribers.

publish method calls all the subscribers subscribed to the publication (provided as a first argument). It calls the subscribers with the data.

Example

import { publish } from 'pusu';
import loadDataPublication from './publications/load-data-publication';

<button
  id="headerRefreshAction"
  onClick={() => {
    // Publish the data
    publish(loadDataPublication, { asOfDate: new Date() });
  }}
>
  Refresh
</button>

Subscribe

declare const subscribe: <T>(publication: TPublication<T>, subscriber: TSubscriber<T>) => (() => void);

Parameters:

• publication: (Required) Object - Publication object created using the api createPublication
• subscriber: (Required) Function - A subscriber function which will be called by the publisher. This function will receive the data published by the publisher.

Return value: Function - A function to unsubscribe, when called then the subscriber is unsubscribed and no longer called by the publisher.

Example

import { subscribe } from 'pusu';
import loadDataPublication from './publications/load-data-publication';

let unsubscribe;

// Subscribe to the publication
unsubscribe = subscribe(loadDataPublication, ({ asOfDate }) => {
  // load the data from API
});

// Unsubscribe from the publication before removal of the component
if (unsubscribe) {
  unsubscribe();
}

Logging

If logging is enabled while creating the pubcalition then each action gets logged.

Log Information

type TLog<T> = {
  publication: string;
  action: TLogAction;
  data?: T;
  meta?: any;
};

• publication: Name of the publication. Default = "Unknown".
• action: "create" | "publish" | "subscribe" | "unsubscribe" | "notify".
• data: Data published and sent to subscribers.
• meta: Can be any metadata. E.g. when a subscriber is notified then the sibscriber function's name is added in the metadata.

Actions

• create: When publication is created.
• publish: When publciation is published with data.
• subscribe: When a subscriber function is subscribed.
• unsubscribe: When a subscriber function is unsubscribed.
• notify: When a subscriber function is called with the data.

Example

createPublication<{ asOfDate: Date }>({ name: 'load-data', enableLogging: process.env.NODE_ENV === 'development' });

Log

'pusu', { publication: 'load-data', action: 'create' }

'pusu', { publication: 'load-data', action: 'subscribe', meta: { subscriber: '[functionName]' } }

'pusu', { publication: 'load-data', action: 'publish', data: { asOfDate: 1706513208749 } }

'pusu', { publication: 'load-data', action: 'notify', data: { asOfDate: 1706513208749 }, meta: { subscriber: '[functionName]' } }

License

MIT