trigger custom events in JS

trigger.js

if (!('CustomEvent' in window)) {
  // For IE 9/10 lol.
  function CustomEvent(eventName, params) {
    params = params || {bubbles: false, cancelable: false, detail: undefined};
    var e = document.createEvent('CustomEvent');
    e.initCustomEvent(eventName, params.bubbles, params.cancelable, params.detail);
    return e;
  }
  CustomEvent.prototype = window.CustomEvent.prototype;
  window.CustomEvent = CustomEvent;
}

function trigger(el, eventName, params) {
  return el.dispatchEvent(new CustomEvent(eventName, params));
}