index.js

var requestFrame = (function () {
  var window = this
  var raf = window.requestAnimationFrame ||
    window.mozRequestAnimationFrame ||
    window.webkitRequestAnimationFrame ||
    function fallbackRAF(func) {
      return window.setTimeout(func, 20)
    }
  return function requestFrameFunction(func) {
    return raf(func)
  }
})()

var cancelFrame = (function () {
  var window = this
  var cancel = window.cancelAnimationFrame ||
    window.mozCancelAnimationFrame ||
    window.webkitCancelAnimationFrame ||
    window.clearTimeout
  return function cancelFrameFunction(id) {
    return cancel(id)
  }
})()

function resizeListener(e) {
  var win = e.target || e.srcElement
  if (win.__resizeRAF__) {
    cancelFrame(win.__resizeRAF__)
  }
  win.__resizeRAF__ = requestFrame(function () {
    var trigger = win.__resizeTrigger__
    trigger.__resizeListeners__.forEach(function (fn) {
      fn.call(trigger, e)
    })
  })
}

var exports = function exports(element, fn) {
  var window = this
  var document = window.document
  var isIE

  var attachEvent = document.attachEvent
  if (typeof navigator !== 'undefined') {
    isIE = navigator.userAgent.match(/Trident/) ||
      navigator.userAgent.match(/Edge/)
  }

  function objectLoad() {
    this.contentDocument.defaultView.__resizeTrigger__ = this.__resizeElement__
    this.contentDocument.defaultView.addEventListener('resize', resizeListener)
  }

  if (!element.__resizeListeners__) {
    element.__resizeListeners__ = []
    if (attachEvent) {
      element.__resizeTrigger__ = element
      element.attachEvent('onresize', resizeListener)
    } else {
      if (getComputedStyle(element).position === 'static') {
        element.style.position = 'relative'
      }
      var obj = (element.__resizeTrigger__ = document.createElement('object'))
      obj.setAttribute(
        'style',
        'display: block; position: absolute; top: 0; left: 0; height: 100%; width: 100%; overflow: hidden; pointer-events: none; z-index: -1; opacity: 0;'
      )
      obj.setAttribute('class', 'resize-sensor')
      obj.__resizeElement__ = element
      obj.onload = objectLoad
      obj.type = 'text/html'
      if (isIE) {
        element.appendChild(obj)
      }
      obj.data = 'about:blank'
      if (!isIE) {
        element.appendChild(obj)
      }
    }
  }
  element.__resizeListeners__.push(fn)
}

module.exports = typeof window === 'undefined' ? exports : exports.bind(window)

module.exports.unbind = function (element, fn) {
  var attachEvent = document.attachEvent
  if (fn) {
    element.__resizeListeners__.splice(
      element.__resizeListeners__.indexOf(fn),
      1
    )
  } else {
    element.__resizeListeners__ = []
  }
  if (!element.__resizeListeners__.length) {
    if (attachEvent) {
      element.detachEvent('onresize', resizeListener)
    } else {
      element.__resizeTrigger__.contentDocument.defaultView.removeEventListener(
        'resize',
        resizeListener
      )
      delete element.__resizeTrigger__.contentDocument.defaultView.__resizeTrigger__
      element.__resizeTrigger__ = !element.removeChild(
        element.__resizeTrigger__
      )
    }
    delete element.__resizeListeners__
  }
}