doriandrn/signal-js

small, simple, fast event system with no dependencies

signal-js

A small (3.9KB minified, 1.5KB gzipped) and fast event system with no dependencies. Written in es6 and built for performance. Great as a pubsub or to add event emitters to your code.

NOTE: Version 2 has landed! Many optimizations have been made and namespace support has been removed. The new code is half the size of the original, is between 200 and 600% faster and has more tests!

Installation

npm install signal-js

How to use

Add a function to signal using on and trigger the function using emit

import signal from 'signal-js';

signal.on('basic', arg => console.log(arg);

signal.emit('basic', 1);
// > 1

Add multiple functions to the same event name

import signal from 'signal-js';

signal.on('multiple', () => console.log(1));
signal.on('multiple', () => console.log(2));
signal.on('multiple', () => console.log(3));

signal.trigger('multiple');
// > 1
// > 2
// > 3

Pass as many parameters as you need

import signal from 'signal-js';

signal.on('params', (one, two, three) => console.log(one, two, three));

signal.emit('params', 1, 2, 3);
// > 1 2 3

Remove events using off

import signal from 'signal-js';

signal.on('test', () => console.log('hi'))
  .off('test') // removes all `test` events
  .emit('test'); // nothing happens

once can also be used

import signal from 'signal-js';

signal.once('bam', function() {
  console.log('Boom!');
});

signal.emit('bam')
// > "Boom!"

signal.emit('bam');
// nothing is logged

The exposed signal is a singleton, but other instances can also be created:

import signal from 'signal-js';

signal.on('foo', () => console.log('global'));

const local = signal();
local.on('foo', () => console.log('local'));

const local2 = local();
local2.on('foo', () => console.log('local2'));

signal.emit('foo');
// > "global"

local.emit('foo');
// > "local"

local2.emit('foo');
// > "local2"

API

.on(eventName, listener)

• eventName string The name of the event
• listener Function The event handler
• Returns: signal

Alias: addListener, subscribe, bind

.off(eventName, listener)

• eventName string The name of the event
• listener Function (optional) The event handler
• Returns: signal

If listener is passed, the specific listener will be unbound, otherwise all listeners under eventName will be unbound.

Alias: removeListener, unsubscribe, unbind

.emit(eventName, [...parameters])

• eventName string The name of the event
• parameters any (optional) The arguments passed to the listener
• Returns: signal

Alias: dispatch, trigger

.once(eventName, listener)

• eventName string The name of the event
• parameters any The event handler
• Returns: signal

Adds a one-time listener that will remove itself after being invoked.

.listeners(eventName)

• eventName string The name of the event
• Returns: Array

Retrieves registered listeners under the eventName. If no eventName is passed, returns all listeners.

.keys()

• Returns: Array

Retrieves all eventNames.

.size(eventName)

• eventName string The name of the event
• Returns: Number

Returns the quantity of listeners at the given eventName. If no eventName is passed, returns the quantity of all listeners.

.disable()

• Returns: signal

Disables the signal. All methods can still be accessed and called. Any calls to emit will be ignored.

.enable()

• Returns: signal Enables the signal.

.clear()

• Returns: signal Removes all listeners and eventNames from the signal.

License

The MIT License (MIT)

Copyright (c) 2018 Joseph Clay

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.