custom event polyfill for IE 11 (>= 9 really)

customevent-polyfill.js

// source: https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent/CustomEvent
;(function() {
  if (typeof window.CustomEvent === "function") return false

  function CustomEvent(event, params) {
    params = params || { bubbles: false, cancelable: false, detail: undefined }
    var evt = document.createEvent("CustomEvent")
    evt.initCustomEvent(event, params.bubbles, params.cancelable, params.detail)
    return evt
  }

  CustomEvent.prototype = window.Event.prototype

  window.CustomEvent = CustomEvent
})()