Dead-simple event handling polyfills. Based largely on http://youmightnotneedjquery.com/

events.js

/**
 * Dead-simple event handling polyfills. Based largely on
 * http://youmightnotneedjquery.com/
 */

/**
 * IE-safe removeEventListener polyfill. Not exported to avoid bugs
 * caused by wrapping the event handler in IE8.
 *
 * @param {Window|Document|HTMLElement} el        Element to listen on
 * @param {String}                      eventName The event to register
 * @param {Function}                    handler   Event handler
 */
function off(el, eventName, handler) {
  if (el.removeEventListener) {
    el.removeEventListener(eventName, handler);
  } else {
    el.detachEvent("on" + eventName, handler);
  }
}

/**
 * IE8-safe addEventListener polyfill
 *
 * @param {Window|Document|HTMLElement} el        Element to listen on
 * @param {String}                      eventName The event to register
 * @param {Function}                    handler   Event handler
 * @return {Function}                             Detaches the handler when called
 */
function on(el, eventName, handler) {
  var h;
  if (el.addEventListener) {
    h = handler;
    el.addEventListener(eventName, handler);
  } else {
    h = function () {
      handler.call(el, window.event);
    };
    el.attachEvent("on" + eventName, h);
  }
  return function detach() {
    if (el) {
      off(el, eventName, h);
      el = h = null;      
    }
  };
}

exports.on = on;