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events.js
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events.js
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"use strict";
// Events implements a declarative event delegation framework.
//
// The constructor works with a WeakMap implementation (can be a
// polyfill). The root DOM node is used for event delegation (all
// events are registered at the root node) except for specific events
// that do not bubble.
class Events {
constructor(WeakMap, root, handler) {
this._elts = new WeakMap();
this._root = root;
this._handler = handler;
this._dispatcher = e => this._dispatch(e);
this._counts = {};
}
update(elt, before, after) {
const b = {};
for (let key in before) b[key.toLowerCase()] = true;
for (let key in after) {
const value = after[key];
key = key.toLowerCase();
if (b[key]) this._update(elt, key, value);
else this._add(elt, key, value);
delete b[key];
}
for (let key in b) this._remove(elt, key);
}
_add(elt, key, value) {
this._elts.set(elt, this._elts.get(elt) || {});
this._elts.get(elt)[key] = value;
if (!this.bubbles(key)) {
elt.addEventListener(key, this._dispatcher);
} else {
const refcount = this._counts[key] || 0;
this._counts[key] = refcount + 1;
if (refcount === 0) this._root.addEventListener(key, this._dispatcher);
}
}
_update(elt, key, value) {
this._elts.get(elt)[key] = value;
}
_remove(elt, key) {
const events = this._elts.get(elt);
if (!events || !events.hasOwnProperty(key)) return;
delete this._elts.get(elt)[key];
if (!this.bubbles(key)) {
elt.removeEventListener(key, this._dispatcher);
} else {
this._counts[key]--;
if (this._counts[key] >= 1) return;
delete this._counts[key];
this._root.removeEventListener(key, this._dispatcher);
}
}
_dispatch(e) {
const events = this._elts.get(e.target);
if (events && events.hasOwnProperty(e.type)) {
return this._handler(e, events[e.type]);
}
this._remove(e.target, e.type);
}
bubbles(eventName) {
const n = eventName;
return n !== "move" && n !== "blur" && n !== "focus";
}
}
exports.Events = Events;