add-event-listener/index.js

add event listeners in IE and ... everywhere else

'use strict'

addEventListener.removeEventListener = removeEventListener
addEventListener.addEventListener = addEventListener

module.exports = addEventListener


// detect passive events
var passive = false

try {
  var opts = Object.defineProperty({}, 'passive', {
    get: function() {
      passive = true
    }
  })

  window.addEventListener('test', null, opts)
  window.removeEventListener('test', null, opts)
} catch(e) {
  passive = false
}


var Events = null

function addEventListener(el, eventName, listener, useCapture) {
  Events = Events || (
    document.addEventListener ?
    {add: stdAttach, rm: stdDetach} :
    {add: oldIEAttach, rm: oldIEDetach}
  )

  return Events.add(el, eventName, listener, useCapture)
}

function removeEventListener(el, eventName, listener, useCapture) {
  Events = Events || (
    document.addEventListener ?
    {add: stdAttach, rm: stdDetach} :
    {add: oldIEAttach, rm: oldIEDetach}
  )

  return Events.rm(el, eventName, listener, useCapture)
}

function stdAttach(el, eventName, listener, useCapture) {
  el.addEventListener(eventName, listener, passive ? useCapture : !!useCapture)
}

function stdDetach(el, eventName, listener, useCapture) {
  el.removeEventListener(eventName, listener, passive ? useCapture : !!useCapture)
}

function oldIEAttach(el, eventName, listener, useCapture) {
  if(useCapture) {
    throw new Error('cannot useCapture in oldIE')
  }

  el.attachEvent('on' + eventName, listener)
}

function oldIEDetach(el, eventName, listener, useCapture) {
  el.detachEvent('on' + eventName, listener)
}