List all active events in a page

event-list.js

// More info at:
// https://www.perimeterx.com/tech-blog/2019/list-every-event-that-exists-in-the-browser/

// Just run it in developer console:
function _isEvent(prop) {
  if (0 !== prop.indexOf("on")) {
    return false;
  }
  return true;
}

function _getEvents(obj) {
  var result = [];
  for (var prop in obj) {
    if (_isEvent(prop)) {
      prop = prop.substr(2); // remove "on" at the beginning
      result.push(prop);
    }
  }
  return result;
}

function getEvents() {
  const result = {};
  result["window"] = _getEvents(window, hasOwnProperty);
  const arr = Object.getOwnPropertyNames(window);
  for (let i = 0; i < arr.length; i++) {
    const element = arr[i];
    let resultArray = [];
    try {
      const obj = window[element];
      if (!obj || !obj["prototype"]) {
        continue;
      }
      proto = obj["prototype"];
      resultArray = _getEvents(proto);
    } catch (err) {
      // console.error(`failed to get events of %o`, element);
    }
    result[element] = resultArray;
  }
  return result;
}

events = getEvents()

const nEvents = Object.values(events).map(e => e.length).reduce((partialSum, a) => partialSum + a, 0)
console.log(`There are ${nEvents} events in your page`)