evtmgr

Helper for managing event handlers

Installing

$ npm install evtmgr
# or
$ bower install evtmgr

Overview

Can be used with anything that emits an event:

• addEventListener
• addListener
• attachEvent
• addEvent

Specifically useful when:

• Adding/removing handlers on a lifecycle hook
• Adding handlers that use bind, and need to be removed
• Conveniently remove all added handlers

Example

React provides a good use case.

import React, { Component } from 'react';
import EventManager from 'evtmgr';

class Menu extends Component {
  constructor(props) {
    super(props);

    this.state = {
      pinned: false
    };

    this.evtmgr = new EventManager();
    this.evtmgr.register(window, 'scroll', this.handleWindowScroll.bind(this));
  }

  componentDidMount() {
    this.evtmgr.attach();
  }

  componentWillUnmount() {
    this.evtmgr.detach();
  }

  handleWindowScroll() {
    this.setState({
      pinned = document.body.scrollTop >= 100
    });
  }

  render() {
    var style = {};
    if (this.state.pinned) {
      style.position = 'fixed';
      style.top = 0;
    } else {
      style.position = 'absolute';
      style.top = 100;
    }

    return (
      <menu style={style}>
        {/*...*/}
      </menu>
    );
  }
}

API

register(obj, type, handler)

Register an event handler

obj

An object that emits an event

type

The event type

handler

The function that handles the event

Example

var EventEmitter = require('events').EventEmitter;
var EventManager = require('evtmgr');
var emitter = new EventEmitter();
var manager = new EventManager();

// Register a single handler
manager.register(emitter, 'someEvent', (e) => {
  console.log('someEvent was fired');
});

// Register handlers for multiple events
manager.register(emitter, {
  insert: (e) => {
    console.log('insert fired');
  },
  update: (e) => {
    console.log('update fired');
  },
  delete: (e) => {
    console.log('delete fired');
  }
});

unregister(obj, type, handler)

Unregister an event handler

obj

An object that emits an event

type

The event type

handler

The function that handles the event

Example

var EventEmitter = require('events').EventEmitter;
var EventManager = require('evtmgr');
var emitter = new EventEmitter();
var manager = new EventManager();

function handleFoo() {}
function handleBar() {}

// Register handlers
manager.register(emitter, {
  foo: handleFoo,
  bar: handleBar
});

// Actually, don't want to handle bar
manager.unregister(emitter, 'bar', handleBar);

attach

Attach registered event handlers to the objects for which they handle events

Attaching can only be done once, so subsequent calls will have no effect, unless detach is called.

Example

// Registration does nothing until attach is called
manager.register(el, 'click', function () {/*...*/});
manager.attach();
// Now el.click() will be handled

detach

Detach registered event handlers from the objects for which they handle events

Example

// Attach all the event handlers
manager.attach();

// Once handlers are no longer wanted
manager.detach();

License

MIT