event-manager

A JavaScript library for managing events. It can be used for front-end and back-end applications.

Installation

NPM

npm install @web-deps/event-manager

Yarn

yarn add @web-deps/event-manager

Usage

Creating an Event Emitter

import { EventEmitter } from "@web-deps/event-manager";

// Subject for events
let form = {
  send: () => {
    console.log("Sending form");
  },
  clear: () => {
    console.log("Clearing form");
  },
  alert: (alertType) => {
    console.log(`Alerting user about ${alertType}.`);
  }
};

const events = ["submit", "success", "failure"];
const formEventManager = new EventEmitter(form, events);

Adding an Observer

//  Import EventEmitter and create an event emitter instance 'formEventManager'

formEventManager.addObserver("submit", ({ name, subject }) => {
  subject.send();
});

Emitting an Event

import { EventEmitter, Event } from "@web-deps/event-manager";

// Create an event emitter and add an observer

formEventManager.emit(new Event("submit"));

// Output: 'Sending form'

API

Event

A class used to create events.

Constructor

Signature

constructor(name, subject [, data]);

Params

• name:
  • Type: string
  • Description: The name of the event.
• subject:
  • Type: object
  • Description: The subject of observation.
• data: (optional)
  • Type: any
  • Description: The data associated with an event.

Properties

• name:
  • Type: string
  • Description: The name of the event.
• subject:
  • Type: object
  • Description: The subject of observation.
• data: (optional)
  • Type: any
  • Description: The data associated with an event.

EventEmitter

A class used to manage events.

Constructor

Signature

constructor(subject, events);

Params

• subject:
  • Type: object
  • Description: The subject of observation.
• events:
  • Type: array of strings
  • Description: The events to be emitted and observed.

Properties

• subject: (readonly)
  • Type: object
  • Description: The subject of observation.
• events: (readonly)
  • Type: array of strings
  • Description: The events to be emitted and observed.
• observers: (readonly)
  • Type: object of functions
  • Description: The observers of events.

Methods

• addObserver:
  • Description: Adds an observer for a particular event.
  • Signature: addObserver(eventName, observer)
  • Params:
    • eventName:
      • Type: string
      • Description: The name of the event to be observed.
    • observer:
      • Type: function
      • Signature: observer(event)
      • Params:
        • event:
          • Type: Event
          • Description: The event emitted.
• removeObserver:
  • Description: Removes an observer for a particular event.
  • Signature: removeObserver(eventName, observer)
  • Params:
    • eventName:
      • Type: string
      • Description: The name of the event observed.
    • observer:
      • Type: function
      • Signature: observer(event)
      • Params:
        • event:
          • Type: Event
          • Description: The event emitted.
• notifyObservers: (protected)
  • Description: Notifies observers of a particular event when the event has been fired.
  • Signature: notifyObservers(eventName [, data])
  • Params:
    • eventName:
      • Type: string
      • Description: The name of the event emitted.
    • data: (optional)
      • Type: any
      • Description: Data associated with the event.
• emit:
  • Description: Emits an event.
  • Signature: emit(eventName [, data])
  • Params:
    • eventName:
      • Type: string
      • Description: The name of the event to emit.
    • data: (optional)
      • Type: any
      • Description: Data associated with the event.
• eventIsRegistered:
  • Description: Checks whether a particular event is registered or not.
  • Signature: eventIsRegistered(eventName)
  • Params:
    • eventName:
      • Type: string
      • Description: The name of the event to be checked.

License

MIT License.