dom-event-handler

A generic DOM event handler implementing the EventListener interface for class methods. Works great in the browser. Does't work great in the Node.js ecosystem.

Installation

$ npm install dom-event-handler

Usage

const DOMEventHandler = require("dom-event-handler")

class MyWSController extends SomeOtherClass {
  constructor () {
    this.ws = new WebSocket('ws://localhost:8080')
    this.handler = new DOMEventHandler(this, this.ws)
  }

  // These methods handle the websocket events
  onmessage (ev) {}
  onopen (ev) {}
  onerror (ev) {}
  onclose (ev) {}
}

Isn't that nicer than this?

const ws = new WebSocket('ws://localhost:8080')

class VerboseWSController {
  constructor () {
    this.foo = 'bar'

    // You have to bind since you don't pass a full context.
    // Static class properties assigned to arrow functions are less verbose
    // but are structurally similar to binding, and have poor env support still.
    // They don't reside on the prototype.  That may or may not matter to the use case.
    this.onmessage = this.onmessage.bind(this)
    this.onopen = this.onopen.bind(this)s
    this.onerror = this.onerror.bind(this)
    this.onclose = this.onclose.bind(this)
  }

  onmessage (ev) {}
  onopen (ev) {}
  onerror (ev) {}
  onclose (ev) {}
}

const c = new VerboseWSController()

ws.addEventListener('message', c.onmessage)
ws.addEventListener('open', c.onopen)
ws.addEventListener('error', c.onerror)
ws.addEventListener('close', c.onclose)

API

handler = new DOMEventHandler(ctx, [node])

Create a new instance of DOMEventHandler passing in a context ctx (often this when created within a class) and optionally a DOM event target node (e.g. an event emitting DOM node) to attach listeners to on instantiation.

The ctx should be an object who's prototype contains event handler methods. Event handler methods must take the form of on{eventname} where eventname is the name of the event you want to listen on and handle (the name you would pass to node.addEventListener). In practice, you can pass a class instance as a ctx, or this when the instance owns the DOMEventHanlder instance.

handler.addEventListeners(node)

Attach all event handler methods on ctx to the DOM event target node.

handler.removeEventListeners(node)

Remove all event handler event names on ctx from the DOM event target node.

Internal Methods

You don't need to call these, but they are there.

handler.handleEvent(event)

Implements the eventListener.handleEvent method for the events found on the ctx prototype. This is where the magic happens.

handler.events

A getter that returns all events found on the ctx the handler is bound to. The events returned from this getter are what get attached and detached in the above methods.

See also

This module was inspired by a @webreflection article.

This is a slick API, but has poor support in the Node.js ecosystem due to poor support for the EventListener interface (Node.js style events do not support handleEvent or similar). For a similar API see node-event-handler, which lacks the bind free benefits of this approach, but can provide a stand-in api when writing universal Node.js code.

License

MIT