Subscribe-events NPM

NOTE: This package has been renamed to `subscribe-easy`

Documentation

Overview

When adding event listeners, often you will need to remove that listener later. If you fail to do so, bugs or memory leaks can occur. The same applies for intervals and timeouts.

To simplify this pattern, use the Subs class in this library. When subscribing to an event or timer through this class, an unsubscribe function is stored and returned. Calling this function will remove the listener.

There is built-in support for subscribing to EventEmitter events and DOM object events, and support for events from custom listener interfaces. There is also support for timeouts and intervals.

This library also includes an easy way to unsubscribe all listeners at once with a single call, and is a perfect complement to React effects.

Features include:

🔔 Quickly and easily subscribe and unsubscribe to events
- An easy way to subscribe and unsubscribe from events in JavaScript.
💁‍♀️ Covers common use cases, as well as custom ones
- Built-in support for EventEmitter and DOM events, and custom.
⏰ Timeout and interval support
- Includes support for setTimeout and setInterval to make life easier.
⚛️ Perfect for React effects
- Makes adding/removing listeners and timers in React effects a breeze.
👍 Simple, flexible, and convenient
- Use static functions yourself via Subscribe, or a Subs instance for ultimate convenience.

Installation

npm i subscribe-events

Quick Start

Create an instance of the Subs class and use that to manage subscriptions.

import { Subs } from 'subscribe-events';

// Use this object to subscribe and unsubscribe
const subs = new Subs();

// ➡️ Event emitter subscription
subs.subscribeEvent(eventEmitter, 'my-event', myEventListener);

// ➡️ DOM event subscription
subs.subscribeDOMEvent(document, 'keypress', keyPressListener);

// ➡️ Custom listener interface subscription
subs.subscribe(() => {
  thing.addObserver(thingObserver);
  return () => thing.removeObserver(thingObserver);
});

// ➡️ setTimeout subscription
subs.setTimeout(() => {
  console.log('Timeout fired!');
}, 2000);

// ➡️ setInterval subscription
subs.setInterval(() => {
  console.log('Interval fired!');
}, 1000);

// ➡️ Push a custom unsubscribe function
subs.push(() => {
  console.log('Custom unsubscribe function!');
});

// You can access all unsub functions directly via `subs.list`
console.log(`There are ${subs.list.length} subscriptions!`);

When it's time to unsubscribe all listeners, call unsubAll():

// Unsubscribe all listeners with one easy call!
subs.unsubAll();

Or, for frameworks like React, you can create a cleanup function that can be called later by using createCleanup():

const cleanup = subs.createCleanup();
// ...
// Unsubscribe all listeners with the cleanup function
cleanup();

Example

Since it's a common use case, below is a full example of adding/removing listeners in React using the Subs class.

In this example, we will subscribe to an event emitter, a DOM event, and a custom listener interface, as well as some timers.

At the end we will return a cleanup function that unsubscribes all listeners and timers using createCleanup().

import React from 'react';
import { EventEmitter } from 'events';

import { Subs } from 'subscribe-events';

export const eventEmitter = new EventEmitter();
export const MyComponent = (props: any) => {
  React.useEffect(() => {
    // Listener functions
    const myEventListener = () => {
      console.log('My event fired!');
    };
    const keyPressListener = (e: any) => {
      console.log('Key pressed!', e);
    };
    const bodySizeListener = (e: any) => {
      console.log('Body size changed!', e);
    };

    // Use this object to subscribe and unsubscribe
    const subs = new Subs();

    // ➡️ Event emitter subscription
    subs.subscribeEvent(eventEmitter, 'my-event', myEventListener);

    // ➡️ DOM event subscription
    subs.subscribeDOMEvent(document, 'keypress', keyPressListener);

    // ➡️ Custom listener interface subscription
    subs.subscribe(() => {
      const resizeObserver = new ResizeObserver(bodySizeListener);
      const targetElement = document.getElementsByTagName('body')[0];
      resizeObserver.observe(targetElement);
      return () => resizeObserver.unobserve(targetElement);
    });

    // ➡️ setTimeout subscription
    subs.setTimeout(() => {
      console.log('Timeout fired!');
    }, 2000);

    // ➡️ setInterval subscription
    subs.setInterval(() => {
      console.log('Interval fired!');
    }, 1000);

    // You can access all unsubscribe functions directly via `subs.list`
    console.log(`There are ${subs.list.length} subscriptions!`);

    // Return a cleanup function that unsubscribes all listeners and timers
    return subs.createCleanup();
  }, []);

  // ...

  return <div>My Component!</div>;
};

Static Functions

If you'd like to call the functions used by Subs manually, you can use the static functions available in the Subscribe class:

import { Subscribe } from 'subscribe-events';

Call any of the following:

Subscribe.subscribe - Call provided function to subscribe to an event and return an unsubscribe function.
Subscribe.subscribeEvent - Subscribe to an emitter event and return an unsubscribe function.
Subscribe.subscribeDOMEvent - Subscribe to a DOM event and return an unsubscribe function.
Subscribe.setTimeout - Create a subscription using setTimeout, return an unsubscribe function.
Subscribe.setInterval - Create a subscription using setInterval, return an unsubscribe function.
Subscribe.unsubAll - Call all provided unsubscribe functions (array or single unsubscribe).
Subscribe.createCleanup - Create and return a cleanup function that, when called, calls all unsubscribe functions provided.

See the JS docs for each for more details.

TypeScript

Type definitions have been included for TypeScript support.

Icon Attribution

Icon by Twemoji.

Contributing

Open source software is awesome and so are you. 😎

Feel free to submit a pull request for bugs or additions, and make sure to update tests as appropriate. If you find a mistake in the docs, send a PR! Even the smallest changes help.

For major changes, open an issue first to discuss what you'd like to change.