EventBusJS

Simple but powerful event bus written in ES2015

Installation

The recommended and the most suitable way to install is through Yarn:

$ yarn add lin3s-event-bus

or alternatively through NPM:

$ npm install --save lin3s-event-bus

Basic Usage

// your-dom-js-file.js

import {onDomReady, onDomLoaded, onWindowResized} from 'lin3s-event-bus';

const onReady = (domReadyEvent) => {
  console.log('DOM is ready!');
};

const onLoaded = (domLoadedEvent) => {
  console.log('window is loaded!');
};

const onResized = (windowResizedEvent) => {
  const
    newWindowHeight = windowResizedEvent.windowWidth,
    newWindowWidth = windowResizedEvent.windowWidth;

  console.log('window is resized!', newWindowWidth, newWindowHeight);
};

onDomReady(onReady);
onDomLoaded(onLoaded);
onWindowResized(onResized);

onDomMutated

This helper method will subscribe to the DomMutatedEventPublisher for DOM injection/removal lookups. Each time a css selector-matching DOM node is added or removed to/from the document's body (by default), or the provided rootNode, your passed callback wil be called. In other words, you will be notified if a DOM node is injected/removed and your provided css selector matches that DOM node.

This is really helpful for defining a component's behaviour independently of the time of the component being added to the page, or unbinding certain logic that referenced that dom node. For example, if we want to trigger some logic, or initialize a component after being injected to the DOM dinamically.

For instance:

// your-dom-js-file.js

import {onDomReady, onDomMutated} from 'lin3s-event-bus';
import MyComponent from './MyComponent';

const LOOKUP_CSS_SELECTOR = '.js-my-component';

const initMyComponent = (domNode) => {
  const myComponent = new MyComponent(domNode);
  
  // Whatever...
};

const onReady = () => {
  const myComponents = document.querySelectorAll(LOOKUP_CSS_SELECTOR);
  
  myComponents.forEach(myComponent => initMyComponent(myComponent));
  
  // `rootNode` is the `document` by default.
  onDomMutated({selector: LOOKUP_CSS_SELECTOR, rootNode: document}, domMutatedEvent => {
    domMutatedEvent.addedNodes.forEach(myComponentNode => initMyComponent(myComponentNode));
    // domMutatedEvent.removedNodes
  });
};

onDomReady(onReady);

Unsubscribing a subscriber

In the following example we are showing how to unsubscribe a previously subscribed subscriber. Every shortcut method returns the associated subscriber, so we can unsubscribe it later on via the LifeTimeEventPublisher or the OneTimeEventPublisher.

// your-dom-js-file.js

import {onWindowResized, LifeTimeEventPublisher} from 'lin3s-event-bus';

const onResized = (windowResizedEvent) => {
  const
    newWindowHeight = windowResizedEvent.windowWidth,
    newWindowWidth = windowResizedEvent.windowWidth;

  console.log('window is resized!', newWindowWidth, newWindowHeight);
};

const windowResizedSubscriber = onWindowResized(onResized);

// later on

LifeTimeEventPublisher.unsubscribe(windowResizedSubscriber);

Usage with priorities

In the following example there are two modules that are listening the WindowResizedEvent event, but the module-b.js is listening the event with higher priority than the module-a.js so, the module-b.js's onResized subscriber always is executed before the module-a.js's subscriber.

// module-a.js

import {onWindowResized} from 'lin3s-event-bus';

const onResized = (windowResizedEvent) => {
  // This will be called after module-a.js onResized callback

  const
    newWindowHeight = windowResizedEvent.windowWidth,
    newWindowWidth = windowResizedEvent.windowWidth;

  console.log('Module A - window is resized!', newWindowWidth, newWindowHeight);
};

onWindowResized(onResized, 0);

// module-b.js

import {onWindowResized} from 'lin3s-event-bus';

const onResized = (windowResizedEvent) => {
  // This will be called before module-b.js onResized callback

  const
    newWindowHeight = windowResizedEvent.windowWidth,
    newWindowWidth = windowResizedEvent.windowWidth;

  console.log('Module B - window is resized!', newWindowWidth, newWindowHeight);
};

onWindowResized(onResized, 1);

Extending the EventBus - Custom Events

In order to extend the Core.Event and publish/subscribe to them, you must firstly implement your custom Event:

// CustomEvent module

import {Core} from 'lin3s-event-bus';

class CustomEvent extends Core.Event {
  
  static NAME = 'YOUR_CUSTOM_EVENT';
  
  constructor(payloadObject) {
    super(CustomEvent.NAME);

    this.payloadObject = payloadObject;
  }
}

export default CustomEvent;

After implementing CustomEvent class, you should code the custom EventSubscriber. Using the previously defined CustomEvent custom event:

// CustomEventSubscriber module

import {Core} from 'lin3s-event-bus';
import CustomEvent from './CustomEvent';

class CustomEventSubscriber extends Core.EventSubscriber {
  constructor(aCallback, aPriority) {
    super(aCallback, aPriority);
  }

  isSubscribedTo(anEvent) {
    // You can define your own custom validation logic. But at least, the event's name must match.
    return anEvent.getName() === event.getName();
  }
}

export default CustomEventSubscriber;

Finally, you should publish the CustomEvent and subscribe to the CustomEvent. If your event will be published more than once you should publish it through the LifeTimeEventPublisher instance. Otherwise, if you need to publish the event just once (for example, a ComponentHasBeenInitializedEvent), you should publish it through the OneTimeEventPublisher instance.

Publishing:

// Publishing the CustomEvent

import {Core} from 'lin3s-event-bus';
// or
import {LifeTimeEventPublisher} from 'lin3s-event-bus';
import {OneTimeEventPublisher} from 'lin3s-event-bus';

import CustomEvent from './CustomEvent';

const payload = {
  // ...
};

const customEvent = new CustomEvent(payload);

Core.LifeTimeEventPublisher.publish(customEvent);
Core.OneTimeEventPublisher.publish(customEvent);
// or
LifeTimeEventPublisher.publish(customEvent);
OneTimeEventPublisher.publish(customEvent);

Subscribing:

// Subscribing to the CustomEvent

import {Core} from 'lin3s-event-bus';
// or
import {LifeTimeEventPublisher} from 'lin3s-event-bus';
import {OneTimeEventPublisher} from 'lin3s-event-bus';

import CustomEventSubscriber from './CustomEventSubscriber';

const customEventSubscriber = new CustomEventSubscriber((customEventInstance) => {
  const payloadObject = customEventInstance.payloadObject;
  
  // Whatever...
});

Core.LifeTimeEventPublisher.subscribe(customEventSubscriber);
Core.OneTimeEventPublisher.subscribe(customEventSubscriber);
// or
LifeTimeEventPublisher.subscribe(customEventSubscriber);
OneTimeEventPublisher.subscribe(customEventSubscriber);

Combined subscriptions

Component initialization

This helper method will be used for fully initializing a component. It will subscribe to the onDomReady and the onDomMutated subscriptions.

import {initComponent} from 'lin3s-event-bus';

initComponent({selector: '.my-css-selector', rootNode: document}, componentDomNode => {
    // Initialize your component with the received componentDomNode node
    // This callback will be executed with each matching node, both on DomReady and on NodeAdded events.
    // ...
});

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