63 lines
1.8 KiB
JavaScript
63 lines
1.8 KiB
JavaScript
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'use strict';
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/* Simplified implementation of DOM2 EventTarget.
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* http://www.w3.org/TR/DOM-Level-2-Events/events.html#Events-EventTarget
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*/
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function EventTarget() {
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this._listeners = {};
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}
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EventTarget.prototype.addEventListener = function(eventType, listener) {
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if (!(eventType in this._listeners)) {
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this._listeners[eventType] = [];
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}
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var arr = this._listeners[eventType];
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// #4
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if (arr.indexOf(listener) === -1) {
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// Make a copy so as not to interfere with a current dispatchEvent.
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arr = arr.concat([listener]);
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}
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this._listeners[eventType] = arr;
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};
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EventTarget.prototype.removeEventListener = function(eventType, listener) {
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var arr = this._listeners[eventType];
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if (!arr) {
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return;
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}
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var idx = arr.indexOf(listener);
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if (idx !== -1) {
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if (arr.length > 1) {
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// Make a copy so as not to interfere with a current dispatchEvent.
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this._listeners[eventType] = arr.slice(0, idx).concat(arr.slice(idx + 1));
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} else {
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delete this._listeners[eventType];
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}
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return;
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}
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};
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EventTarget.prototype.dispatchEvent = function() {
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var event = arguments[0];
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var t = event.type;
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// equivalent of Array.prototype.slice.call(arguments, 0);
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var args = arguments.length === 1 ? [event] : Array.apply(null, arguments);
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// TODO: This doesn't match the real behavior; per spec, onfoo get
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// their place in line from the /first/ time they're set from
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// non-null. Although WebKit bumps it to the end every time it's
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// set.
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if (this['on' + t]) {
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this['on' + t].apply(this, args);
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}
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if (t in this._listeners) {
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// Grab a reference to the listeners list. removeEventListener may alter the list.
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var listeners = this._listeners[t];
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for (var i = 0; i < listeners.length; i++) {
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listeners[i].apply(this, args);
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}
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}
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};
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module.exports = EventTarget;
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