Suggestion - Using WeakMap() for EventCache

[cyfung1031]

In the lastest release,

var eventsNamespace = '___ce',
...
function getEventsCache(ele) {
  return ele[eventsNamespace] = ele[eventsNamespace] || {};
}

This was the old way to bind the data to DOM. Two problems would be created ...

1. coding is possible to get crashed if other part of the script used eventsNamespace too.
2. possible memory leak - GC for the eventsCache

According to caniuse, >95% browsers can use WeakMap(). (all modern browsers released after 2015)
It is worth to use WeakMap() to avoid problems.

var eventsCaches = new WeakMap(),
...
function getEventsCache(ele) {
  return eventsCaches.get(ele) || (eventsCaches.set(ele, ele={}), ele);
}

[fabiospampinato]

Good idea, we should switch to that eventually.