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A universal, human-centric, replayable javascript event emitter.

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A universal, human-centric, replayable event emitter.

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The world just like software is full of events. Sometimes these events occur while we are busy doing other things. Wouldn't it be nice to have a way to replay all events? Noel is the way.

By being able to replay events we can design reactive systems without having to worry about timing.

For example, code like

// Check if there is a user in case we missed the userChanged event
const user = sessionService.getUser();
if(user) updateAvatarPhoto(user)

// Listen for further changes

can become


Meaning that if the userChanged event was already fired, it will be replayed with the last arguments and if it gets fired again, we'll be listening.


  • Event replaying. Never miss a beat.
  • API designed for humans. No useless concepts to try to make sense of.


npm install noel


Creating a noel instance

const Noel = require('Noel');

const noel = new Noel();

Emitting and listening to events

// Listen for an event
noel.on('friday', partyAllNightLong);

// Emit an event
noel.emit('friday', arg1, arg2 ....);

Replaying events

// Replay an event once
noel.on(eventName, eventListener).replay();

// Replay an event x amount of times
noel.on(eventName, eventListener).replay(x);

Disabling replay

// When creating the noel instance
const noel = new Noel({
    replay: false

// At runtime

Enabling replay

Please do note that replay is enabled by default, so this should only be necessary if it was disabled at runtime.

// At runtime

Removing an event listener

noel.removeListener(eventName, eventListener);

or if you save a reference to the eventManager

const eventManager = noel.on('myEvent', eventListener);
// ... 

Removing all event listeners

noel.removeAllListeners(eventName, eventListener);

Clearing an event replay buffer

If you would like to clear all saved event emissions for replay


Clearing all events replay buffers

If you would like to clear all saved events emissions for replay


Changing the events replay buffer size

Or in human words, changing the amount of event emissions that are saved for replays.

Default is 1.

// When creating the noel instance
const noel = new Noel({
    replayBufferSize: aNewBufferSize

// ...

// At runtime

Disabling the no event listeners warning

When an event is emitted, no listeners have been set AND the replay was disabled so there is no way of doing anything with the emission, a warning will be logged into the console if available. To disable this behaviour:

// When creating the noel instance
const noel = new Noel({
    noEventListenersWarning: false

// ...

// At runtime

Enabling the no event listeners warning

Please do note that the no event listeners warning is enabled by default, so this should only be necessary if it was disabled at runtime.



Clone the repository

git clone [email protected]:lifenautjoe/noel.git

Use npm commands

  • npm t: Run test suite
  • npm start: Runs npm run build in watch mode
  • npm run test:watch: Run test suite in interactive watch mode
  • npm run test:prod: Run linting and generate coverage
  • npm run build: Generate bundles and typings, create docs
  • npm run lint: Lints code
  • npm run commit: Commit using conventional commit style (husky will tell you to use it if you haven't :wink:)

Author Joel Hernandez

Open Source Agenda is not affiliated with "Noel" Project. README Source: lifenautjoe/noel

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